Humanized anti-interleukin 3 receptor alpha chain antibodies

ABSTRACT

The present disclosure provides antibodies that bind to interleukin-3 receptor alpha chain and uses thereof.

RELATED APPLICATION DATA

The present application claims priority from U.S. Patent Application No.61/374,489 entitled “Humanized Anti-Interleukin 3 Receptor Alpha ChainAntibodies” filed on 17 Aug. 2010 and from International PatentApplication No: PCT/AU2011/000155 entitled “Compositions and Methods forTargeting Type 1 Interferon Producing Cells”. The entire contents ofthese applications are hereby incorporated by reference.

FIELD

The present disclosure relates to anti-interleukin 3 receptor alphachain antibodies and uses thereof.

BACKGROUND

The functional interleukin 3 receptor is a heterodimer that comprises aspecific alpha chain (IL-3Rα; CD123) and a “common” IL-3 receptor betachain (β_(c); CD131) that is shared with the receptors for granulocytemacrophage colony stimulating factor (GM-CSF) and interleukin 5 (IL-5).

IL-3Rα is a type I transmembrane protein with a deduced Molecular Weightof about 41 kDa containing an extracellular domain involved in IL-3binding, a transmembrane domain and a short cytoplasmic tail of about 50amino acids. The extracellular domain is composed of two regions: anN-terminal region of about 100 amino acids, the sequence of whichexhibits similarity to equivalent regions of the GM-CSF and IL-5receptor alpha-chains; and a region proximal to the transmembrane domainthat contains four conserved cysteine residues and a WSXWS motif commonto other members of this cytokine receptor family.

The IL-3 binding domain comprises about 200 amino acid residue cytokinereceptor motifs (CRMs) made up of two Ig-like folding domains. Theextracellular domain of IL-3Rα is highly glycosylated, withN-glycosylation necessary for both ligand binding and receptorsignaling.

IL-3Rα is expressed widely throughout the hematopoietic system includinghematopoietic progenitors, mast cells, erythroid cells, megakaryocytes,basophils, eosinophils, monocytes/macrophages, neutrophils and CD5⁺B-lymphocytes. Non-hematopoictic cells such as plasmacytoid dendriticcells (pDCs), Leydig cells, endothelial cells and stromal cells alsoexpress IL-3Rα.

IL-3Rα is also expressed by cells involved in certain disease statesincluding myelodysplastic syndrome, mycloid leukemia (for example, acutemyclogenous leukemia (AML)), malignant lymphoproliferative disorderssuch as lymphoma, allergies and autoimmune disease, such as lupus,Sjögren's syndrome or sclerodenna. Accordingly, anti-IL-3Rα antibodiesare desirable for therapeutic applications.

SUMMARY

The present disclosure is based on the inventor's production of ahumanized antibody that binds specifically to IL-3Rα. Followinghumanization, the inventor found that the affinity of the antibody forIL-3Rα was reduced. Accordingly, the inventor performed affinitymaturation to improve the affinity of the antibody for IL-3Rα.Unpredictably, the affinity matured antibody included mutations in theframework regions (FRs) of the heavy chain variable region (V_(H)) andlight chain variable region (V_(L)), as well as in CDR1 of the lightchain.

The inventor also produced forms of this antibody capable of inducingenhanced levels of effector function.

The inventor also found that a particular modification to induceenhanced effector function resulted in an additional desirable propertyin that following administration of the modified antibody to a mammalthe number of NK cells in the mammal were initially reduced, howeverthen expanded to levels greater than prior to administration. Theinventor has also shown that there is a correlation between the numberof NK cells and lysis of target cells, e.g., leukemia cells.

The present disclosure is broadly directed to an immunoglobulin based ona murine antibody capable of specifically binding to an II-3Rα chain.

In one example, the present disclosure provides an isolated orrecombinant immunoglobulin that specifically binds to an IL-3Rα chainand comprises complementarity determining regions (CDRs) of a V_(L)comprising a sequence set forth in SEQ ID NO: 8 and CDRs of a V_(H) setforth in SEQ ID NO: 9.

The present disclosure additionally or alternatively provides anisolated or recombinant antibody or antigen binding fragment thereof,the antibody or antigen binding fragment capable of specifically bindingto IL-3Rα chain and comprising CDRs of a V_(L) comprising a sequence setforth in SEQ ID NO: 8 and CDRs of a V_(H) set forth in SEQ ID NO: 9.

The present disclosure additionally or alternatively provides anisolated or recombinant humanized antibody or antigen binding fragmentthereof, the antibody or antigen binding fragment capable ofspecifically binding to IL-3Rα chain and comprising CDRs of a V_(L)comprising a sequence set forth in SEQ ID NO: 8 and CDRs of a V_(H) setforth in SEQ ID NO: 9.

In one example, the present disclosure provides an isolated orrecombinant immunoglobulin that specifically binds to an IL-3Rα chainand comprises amino acid sequences according to SEQ ID NOs: 2-7,respectively.

The present disclosure additionally or alternatively provides anisolated or recombinant antibody or antigen binding fragment thereof,the antibody or antigen binding fragment capable of specifically bindingto II-3Rα chain and comprising amino acid sequences according to SEQ IDNOs: 2-7.

The present disclosure additionally or alternatively provides anisolated or recombinant humanized antibody or antigen binding fragmentthereof, the antibody or antigen binding fragment capable ofspecifically binding to IL-3Rαchain and comprising amino acid sequencesaccording to SEQ ID NOs: 2-7.

For example, the immunoglobulin or antibody comprises:

(i) a light chain variable region (V_(L)) comprising CDRs 1, 2 and 3 asset forth in SEQ ID NOs: 2, 3 and 4, respectively; and(ii) a heavy chain variable region (V_(H)) comprising CDRs 1, 2 and 3 asset forth in SEQ ID NOs: 5, 6 and 7, respectively.

For example, the immunoglobulin or antibody comprises:

(i) a V_(L) comprising:

a) a CDR1 comprising a sequence set forth in SEQ ID NO: 2 (or encoded bya sequence set forth in SEQ ID NO: 14);

b) a CDR2 comprising a sequence set forth in SEQ ID NO: 3 (or encoded bya sequence set forth in SEQ ID NO: 15); and

c) a CDR3 comprising a sequence set forth in SEQ ID NO: 4 (or encoded bya sequence set forth in SEQ ID NO: 16); and

(ii) a V_(H) comprising:

d) a CDR1 comprising a sequence set forth in SEQ ID NO: 5 (or encoded bya sequence set forth in SEQ ID NO: 17);

e) a CDR2 comprising a sequence set forth in SEQ ID NO: 6 (or encoded bya sequence set forth in SEQ ID NO: 18); and

f) a CDR3 comprising a sequence set forth in SEQ ID NO: 7 (or encoded bya sequence set forth in SEQ ID NO: 19).

The present disclosure additionally or alternatively provides anisolated or recombinant humanized antibody or antigen binding fragmentthereof, the antibody or antigen binding fragment capable ofspecifically binding to IL-3Rα chain and comprising a V_(L) comprisingan amino acid sequence according to SEQ ID NO: 8 (or encoded by asequence set forth in SEQ ID NO: 20) and/or a V_(H) comprising an aminoacid sequence according to SEQ ID NO: 9 (or encoded by a sequence setforth in SEQ ID NO: 21).

The present disclosure additionally or alternatively provides anisolated or recombinant humanized antibody or antigen binding fragmentthereof, the antibody or antigen binding fragment capable ofspecifically binding to IL-3Rαchain and comprising a V_(L) comprising anamino acid sequence according to SEQ ID NO: 8 (or encoded by a sequenceset forth in SEQ ID NO: 20) and a V_(H) comprising an amino acidsequence according to SEQ ID NO: 9 (or encoded by a sequence set forthin SEQ ID NO: 21).

Exemplary antigen binding fragments contemplated by the presentdisclosure include:

-   (i) a domain antibody (dAb);-   (ii) aFv;-   (iii) a scFv or stabilized form thereof (e.g., a disulfide    stabilized scFv);-   (iv) a dimeric scFv or stabilized form thereof;-   (v) a diabody, triabody, tetrabody or higher order multimer,-   (vi) Fab fragment;-   (vii) a Fab′ fragment;-   (viii) a F(ab′) fragment;-   (ix) a F(ab′b) fragment;-   (x) any one of (i)-(ix) fused to a Fc region of an antibody;-   (xi) any one of (i)-(ix) fused to an antibody or antigen binding    fragment thereof that binds to an immune effector cell.

In one example, the immunoglobulin or antibody depletes or at leastpartly eliminates cells to which it binds, e.g., leukemic cells and/orbasophils and/or pDCs.

As will be apparent to the skilled artisan from the disclosure herein,exemplary immunoglobulins or antibodies are capable of depleting or atleast partly eliminating cells to which it binds without beingconjugated to a toxic compound.

In one example, the immunoglobulin or antibody is capable of inducing aneffector function, e.g., an effector function that results in killing acell to which the immunoglobulin or antibody binds. Exemplary effectorfunctions include ADCC, antibody-dependent cell-mediated phagocytosis(ADCP) and/or complement-dependent cytotoxicity (CDC).

In one example, the immunoglobulin or antibody is capable of inducingADCC.

In one example, the immunoglobulin or antibody comprises an antibody Fcregion capable of inducing an effector function. For example, theeffector function is Fc-mediated effector function. In one example, theFc region is an IgG1 Fc region or an IgG3 Fc region or a hybridIgG1/IgG2 Fec region.

In one example, the immunoglobulin or antibody is capable of inducing asimilar (e.g., not significantly different or within about 10%) or thesame level of effector function as a wild-type human IgG1 and/or humanIgG3 Fc region.

In one example, the immunoglobulin or antibody is capable of inducing anenhanced level of effector function.

In one example, the level of effector function induced by theimmunoglobulin or antibody is enhanced relative to that of theimmunoglobulin or antibody when it comprises a wild-type IgG1 Fc region.

In one example the immunoglobulin or antibody is afucosylated orcomprises a FPc region that is afucosylated.

In another example, the immunoglobulin or antibody has a lower level offucosylation compared to an immunoglobulin or antibody produced by ahuman or a CHO cell that has not been altered to reduce the level offucosylation of proteins.

In accordance with this example, a lower level of fucosylation will beunderstood to mean that in a composition comprising the immunoglobulinor antibody the percentage of fucosylated immunoglobulins (e.g.,glycosyl groups attached to Asn297 of an antibody comprising fucose) islower than produced by a human or a CHO cell that has not been alteredto reduce the level of fcosylation of proteins.

For example, the immunoglobulin or antibody is an afucosylated humanizedantibody comprising a V_(L) comprising a sequence set forth in SEQ IDNO: 8 (or encoded by a sequence set forth in SEQ ID NO: 20) and a V_(H)comprising a sequence set forth in SEQ ID NO: 9 (or encoded by asequence set forth in SEQ ID NO: 21). For example, the immunoglobulin orantibody is an afucosylated humanized antibody comprising a light chaincomprising a sequence set forth in SEQ ID NO: 13 (or encoded by asequence set forth in SEQ ID NO: 23) and a heavy chain comprising asequence set forth in SEQ ID NO: 10 (or encoded by a sequence set forthin SEQ ID NO: 22).

In one example, the immunoglobulin or antibody is a humanized antibodycomprising a light chain comprising a sequence set forth in SEQ ID NO:13 (or encoded by a sequence set forth in SEQ ID NO: 23) and a heavychain comprising a sequence set forth in SEQ ID NO: 10 (or encoded by asequence set forth in SEQ ID NO: 22) expressed by a mammalian cell(e.g., a CHO cell) that does not express detectable levels of (orexpresses reduced levels of) α-1,6-fucosyltransferase (FUT8).

In one example, the immunoglobulin or antibody comprises an Fc regioncomprising one or more amino acid sequence substitutions that enhancethe effector function induced by the immunoglobulin. For example, theone or more amino acid sequence substitutions increase the affinity ofthe Fc region for a Fcγ receptor (FcγR) compared to a Fc region notcomprising the substitutions. For example, the one or more amino acidsubstitutions enhance increase the affinity of the Fc region for a FcγRselected from the group consisting of FcγRI, FcγRIIa, FcγRIIe andFcγRIIa compared to a Fc region not comprising the substitutions. In oneexample, the one or more amino acid sequence substitutions are:

(i) S239D, A330L and I332E according to the EU numbering system ofKabat; or(ii) S239D and I332E according to the EU numbering system of Kabat.

For example, the immunoglobulin or antibody is a humanized antibodycomprising a V_(L) comprising a sequence set forth in SEQ ID NO: 8 (orencoded by a sequence set forth in SEQ ID NO: 20) and a V_(H) comprisinga sequence set forth in SEQ ID NO: 9 (or encoded by a sequence set forthin SEQ ID NO: 21), wherein the antibody comprises a Fc region comprisingone or more amino acid sequence substitutions selected from the groupconsisting of:

(i) S239D, A330L and I332E according to the EU numbering system ofKabat; and(ii) S239D and I332E according to the EU numbering system of Kabat.

In one example, the Fc region comprises a sequence set forth betweenresidues 234-450 of SEQ ID NO: 11 (comprising the S239D and I332Esubstitutions according to the EU numbering system of Kabat).

In one example, the Fc region comprises a sequence set forth betweenresidues 234-450 of SEQ ID NO: 12 (comprising the S239D, A330L and I332Esubstitutions according to the EU numbering system of Kabat).

In one example, the immunoglobulin or antibody is selected from thegroup consisting of:

(i) an antibody comprising a light chain comprising a sequence set forthin SEQ ID NO: 13 and a heavy chain comprising a sequence set forth inSEQ ID NO: 11;(ii) an antibody comprising a comprising a light chain comprising asequence set forth in SEQ ID NO: 13 and a heavy chain comprising asequence set forth in SEQ ID NO: 12.

As discussed herein above, the inventor has determined that followingadministration of an antibody described herein, the number of NK cellsin circulation in a mammal are initially reduced and then increasedcompared to the number of NK cells in circulation in the mammal prior toadministration. The inventor has also shown that increasing the numberof NK cells relative to target cells results in increased efficacy,i.e., a greater number of target cells are killed. This effect isinduced by an antibody comprising a constant region or Fc regioncomprising amino acid substitutions S239D and I332E according to the EUnumbering system of Kabat.

Thus, in one example, the present disclosure provides an isolated orrecombinant antibody, which is capable of specifically binding to IL-3Rαchain and comprising:

(i) a light chain variable region (V_(L)) comprising CDRs 1, 2 and 3 asset forth in SEQ ID NOs: 2, 3 and 4, respectively;(ii) a heavy chain variable region (V_(H)) comprising CDRs 1, 2 and 3 asset forth in SEQ ID NOs: 5, 6 and 7, respectively, and(iii) a heavy chain constant region comprising amino acid substitutionsS239D and I332E according to the EU numbering system of Kabat

In one example, the present disclosure provides an isolated orrecombinant humanized antibody, the antibody capable of specificallybinding to IL-3Rα chain and comprising:

(i) a V_(L) comprising:

a) a CDR1 comprising a sequence set forth in SEQ ID NO: 2 (or encoded bya sequence set forth in SEQ ID NO: 14);

b) a CDR2 comprising a sequence set forth in SEQ ID NO: 3 (or encoded bya sequence set forth in SEQ ID NO: 15); and

c) a CDR3 comprising a sequence set forth in SEQ ID NO: 4 (or encoded bya sequence set forth in SEQ ID NO: 16);

(ii) a V_(H) comprising:

d) a CDR1 comprising a sequence set forth in SEQ ID NO: 5 (or encoded bya sequence set forth in SEQ ID NO: 17);

e) a CDR2 comprising a sequence set forth in SEQ ID NO: 6 (or encoded bya sequence set forth in SEQ ID NO: 18); and

f) a CDR3 comprising a sequence set forth in SEQ ID NO: 7 (or encoded bya sequence set forth in SEQ ID NO: 19); and

(iii) a heavy chain constant region comprising amino acid substitutionsS239D and I332E according to the EU numbering system of Kabat.

In one example, the heavy chain constant region is a hybrid of a humanIgG1 and a human IgG2 constant regions.

In one example, the constant region comprises a sequence set forthbetween residues 121-450 (inclusive) of SEQ ID NO: 11.

The present disclosure additionally or alternatively provides anisolated or recombinant humanized antibody, the antibody capable ofspecifically binding to IL-3Rα chain and comprising:

(i) a V_(L) comprising an amino acid sequence according to SEQ ID NO: 8(or encoded by a sequence set forth in SEQ ID NO: 20) and/or a V_(H)comprising an amino acid sequence according to SEQ ID NO: 9 (or encodedby a sequence set forth in SEQ ID NO: 21); and(ii) a heavy chain constant region comprising amino acid substitutionsS239D and I332E according to the EU numbering system of Kabat.

In one example, the heavy chain constant region is a hybrid of a humanIgG1 and a human IgG2 constant regions.

In one example, the constant region comprises a sequence set forthbetween residues 121-450 (inclusive) of SEQ ID NO: 11.

The present disclosure additionally or alternatively provides anisolated or recombinant humanized antibody, the antibody capable ofspecifically binding to IL-3Rα chain and comprising a V_(L) comprisingan amino acid sequence according to SEQ ID NO: 8 (or encoded by asequence set forth in SEQ ID NO: 20), a V_(H) comprising an amino acidsequence according to SEQ ID NO: 9 (or encoded by a sequence set forthin SEQ ID NO: 21) and a heavy chain constant region comprising aminoacid substitutions S239D and I332E according to the EU numbering systemof Kabat.

In one example, the heavy chain constant region is a hybrid of a humanIgG1 and a human IgG2 constant regions.

In one example, the constant region comprises a sequence set forthbetween residues 121-450 (inclusive) of SEQ ID NO: 11

In one example, the present disclosure provides an isolated orrecombinant humanized antibody, the antibody capable of specificallybinding to IL-3Rα chain and comprising a light chain comprising asequence set forth in SEQ ID NO: 13 and a heavy chain comprising asequence set forth in SEQ ID NO: 11.

In one example, an immunoglobulin or antibody or antigen bindingfragment thereof of the present disclosure neutralizes IL-3 signaling.

In one example, an immunoglobulin or antibody of the present disclosureis a naked immunoglobulin or an antibody or antigen binding fragmentthereof of the present disclosure is a naked antibody or antigen bindingfragment thereof.

In one example, an immunoglobulin or antibody of the present disclosureis a full length antibody.

In one example, an immunoglobulin or antibody of the present disclosurebinds to IL-3Rα chain with an equilibrium dissociation constant (K_(D))of 1×10⁻⁹ M or less, such as 5×10⁻⁹ M or less, for example, 3×10⁻⁹ M orless, such as 2.5×10⁻⁹ M or less.

In one example, an immunoglobulin or antibody of the present disclosurebinds to IL-3Rα chain with a K_(D) of about 2.2×10⁻⁹ M or less. In oneexample, the K_(D) is between about 1×10⁻⁹ M and about 2.5×10⁻⁹ M, forexample is about 2.2×10⁻⁹ M.

In one example, an immunoglobulin or antibody of the present disclosurebinds to IL-3Rα chain with a K_(D) of about 9×10⁻⁹M or less, forexample, about 8×10⁻⁹ M or less. In one example, the K_(D) is betweenabout 5×10⁻¹⁰ M and about 9×10⁻¹⁰ M, for example is about 7.8×10⁻¹⁰ M.

The disclosure also includes fragments, variants and derivatives of theimmunoglobulin or antibody of the disclosure.

In one example, an immunoglobulin or antibody of the present disclosureis capable of reducing the number of NK cells when administered to amammal (e.g., a non-human primate, such as a cynomolgus monkey). Forexample, the immunoglobulin or antibody is capable of reducing thenumber of NK cells when administered to the mammal by at least about20%, such as at least about 30% or 40% within 12 hours or 10 hours or 8hours of administration. For example, the immunoglobulin or antibody iscapable of reducing the number of NK cells when administered to themammal by at least about 50% within 6 hours of administration. In oneexample, the immunoglobulin or antibody is capable of reducing thenumber of NK cells when administered at a dose of between 0.0001 mg/kgand 50 mg/kg, such as between about 0.0005 mg/kg and about 40 mg/kg, forexample, between about 0.001 mg/kg and about 30 mg/kg, such as about0.005 mg/kg and about 20 mg/kg, such as about 0.01 mg/kg and about 10mg/kg. For example, the immunoglobulin or antibody is capable ofreducing the number of NK cells when administered to the mammal by atleast about 50% within 6 hours of administration when administered at adose of about 0.01 mg/kg or 0.1 mg/kg or 1 mg/kg or 10 mg/kg. In oneexample, the dose is about 0.01 mg/kg or 0.1 mg/kg.

In one example, the number of NK cells in the mammal is increased about7 or 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19or 20 or 22 or 29 or 57 days after administering the immunoglobulin orantibody compared to the number of NK cells in the mammal prior toadministration of the immunoglobulin or antibody. For example, thenumber of NK cells is increased at least about 8 or 11 or 17 or 22 or 29days after administration. For example, the number of NK cells in themammal is increased by about 10% or 20% or 30% or 50% or 60% or 70% or80% compared to the number of NK cells in the mammal prior toadministration of the immunoglobulin or antibody. For example, thenumber of NK cells in the mammal is increased by about 20% at least 8days after administration of the antibody or immunoglobulin at a dosebetween 0.001 mg/kg and 0.1 mg/kg compared to the number of NK cells inthe mammal prior to administration of the immunoglobulin or antibody.For example, the number of NK cells in the mammal is increased by about50% at least 11, 17, 22 or 29 days after administration of the antibodyor immunoglobulin at a dose between 0.001 mg/kg and 0.1 mg/kg comparedto the number of NK cells in the mammal prior to administration of theimmunoglobulin or antibody. In one example, the antibody orimmunoglobulin is administered at a dose of between 0.01 mg/kg and 0.1mg/kg. For example, the immunoglobulin or antibody is administered at adose of 0.01 mg/kg or 0.1 mg/kg.

Based on the disclosure herein, it will be apparent to the skilledartisan that the present disclosure provides an immunoglobulin orantibody that, when administered to a mammal, causes an increase in thenumber of NK cells in the mammal. For example, the immunoglobulin orantibody, when administered to a mammal, causes a reduction in thenumber of NK cells in the mammal followed by an increase in the numberof NK cells. In one example, the number of NK cells is increased orreduced compared to the number of NK cells in the mammal prior toadministration of the immunoglobulin or antibody.

In one example, the immunoglobulin or antibody is capable of reducingthe number of NK cells in the mammal by at least about 50% within 6hours of administration when administered at a dose of about 0.01 mg/kgor 0.1 mg/kg and the number of NK cells in the mammal is increased byabout 20% at least 8 days after administration of the antibody orimmunoglobulin at a dose between 0.001 mg/kg and 0.1 mg/kg compared tothe number of NK cells in the mammal prior to administration of theimmunoglobulin or antibody.

In one example, the disclosure provides a pharmaceutical compositioncomprising an immunoglobulin or antibody according to the presentdisclosure and a pharmaceutically acceptable carrier, diluent orexcipient.

The present disclosure also provides an isolated nucleic acid encodingan immunoglobulin or antibody of the present disclosure.

Exemplary sequences of nucleic acids are discussed in the context ofencoding antibodies or immunoglobulins of the disclosure and are to betaken to apply mutatis mutandis to the present example of thedisclosure.

The present disclosure also provides a nucleic acid capable ofhybridizing to a nucleic acid of the disclosure under high stringencyhybridization conditions.

The disclosure also includes fragments, homologs and derivatives of anisolated nucleic acid of the disclosure.

The present disclosure also provides a genetic construct comprising anisolated nucleic acid of the disclosure and one or more additionalnucleotide sequences, such as a promoter operably linked to the nucleicacid.

In one example, the genetic construct is an expression constructcomprising an expression vector and an isolated nucleic acid of thedisclosure, wherein said isolated nucleic acid is operably linked to oneor more regulatory nucleic acids in said expression vector.

In one example, the genetic construct of the disclosure comprises anucleic acid encoding a polypeptides (e.g., comprising a V_(H)) operablylinked to a promoter and a nucleic acid encoding another polypeptide(e.g., comprising a V_(L)) operably linked to a promoter.

In another example, the genetic construct is a bicistronic geneticconstruct, e.g., comprising the following operably linked components in5′ to 3′ order:

(i) a promoter(ii) a nucleic acid encoding a first polypeptide;(iii) an internal ribosome entry site; and(iv) a nucleic acid encoding a second polypeptide.

For example, the first polypeptide comprises a V_(H) and the secondpolypeptide comprises a V_(L), or the first polypeptide comprises aV_(L) and the second polypeptide comprises a V_(H).

The present disclosure also contemplates separate genetic constructs oneof which encodes a first polypeptide (e.g., comprising a V_(H)) andanother of which encodes a second polypeptide (e.g., comprising aV_(L)). For example, the present disclosure also provides a compositioncomprising:

(i) a first expression construct comprising a nucleic acid encoding apolypeptide (e.g., comprising a V_(H)) operably linked to a promoter,and(ii) a second expression construct comprising a nucleic acid encoding apolypeptide (e.g., comprising a V_(L)) operably linked to a promoter.

The disclosure also provides a host cell comprising a genetic constructaccording to the present disclosure.

In one example, the present disclosure provides an isolated cellexpressing an immunoglobulin or antibody or antigen binding fragment ofthe disclosure or a recombinant cell genetically-modified to express theimmunoglobulin, antibody or antigen binding fragment.

In one example, the cell comprises the genetic construct of thedisclosure or:

(i) a first genetic construct comprising a nucleic acid encoding apolypeptide (e.g., comprising a V_(H)) operably linked to a promoter;and(ii) a second genetic construct comprising a nucleic acid encoding apolypeptide (e.g., comprising a V_(L)) operably linked to a promoter,wherein the first and second polypeptides form an immunoglobulin,antibody or antigen binding fragment of the present disclosure.

The genetic construct can be integrated into the cell or remainepisomal.

Examples of cells of the present disclosure include bacterial cells,yeast cells, insect cells or mammalian cells.

The present disclosure additionally provides a method for producing animmunoglobulin, antibody or antigen binding fragment of the disclosure,the method comprising maintaining the genetic construct(s) of thedisclosure under conditions sufficient for the immunoglobulin, antibodyor antigen binding fragment to be produced.

In one example, the method for producing an immunoglobulin, antibody orantigen binding fragment of the disclosure comprises culturing the cellof the disclosure under conditions sufficient for the immunoglobulin,antibody or antigen binding fragment to be produced and, optionally,secreted.

In one example, the method for producing an immunoglobulin, antibody orantigen binding fragment of the disclosure additionally comprisesisolating the immunoglobulin, antibody or antigen binding fragment.

The present disclosure additionally provides a method of producing arecombinant immunoglobulin or antibody of the disclosure, the methodincluding the steps of:

(i) culturing a host cell containing an expression vector according tothe disclosure such that the recombinant immunoglobulin or antibody isexpressed in said host cell; and(ii) isolating the recombinant immunoglobulin.

In one example, a method for producing an immunoglobulin, antibody orantigen binding fragment of the disclosure additionally comprisesformulating the immunoglobulin, antibody or antigen binding fragmentwith a pharmaceutically acceptable carrier.

The present disclosure also provides a method of prophylactic ortherapeutic treatment of a disease or condition in a mammal, the methodincluding the step of administering the immunoglobulin or antibody ofthe disclosure to the mammal to thereby treat or prevent the disease orcondition.

In one example, the mammal is a human.

In one example, the mammal is in need of treatment or prophylaxis.

In one example, the mammal in need suffers from the disease orcondition.

In one example, the mammal in need is at risk of developing the diseaseor condition or a relapse thereof.

The present disclosure also provides for use of an immunoglobulin,antibody or antigen binding fragment of the disclosure or a compositionof the disclosure in medicine.

The present disclosure additionally or alternatively provides for use ofan immunoglobulin, antibody or antigen binding fragment of thedisclosure in the manufacture of a medicament for the treatment of adisease or condition in a mammal.

The present disclosure also provides an immunoglobulin, antibody orantigen binding fragment of the disclosure for use in the treatment of adisease or condition in a mammal.

In one example, the disease or condition is an IL3Rα-mediated disease orcondition.

In one example, the disease or condition is myelodysplastic syndrome.

In one example, the disease or condition is cancer, such as ahematologic cancer, for example, leukemia, such as an acute leukemia(e.g., acute myclogenous leukemia) or a chronic leukemia (e.g., chronicmyelomonocytic leukemia).

In one example, the disease or condition is an IL-3Rα-associated cancer,e.g., leukemia, i.e., the cancer (or leukemia) is characterized bycancer (or leukemia) cells expressing IL-3Rα.

In another example, the cancer is a malignant lymphoproliferativedisorder such as lymphoma.

In one example, the disease or condition is an autoimmune condition oran inflammatory condition. For example, the condition is lupus, e.g.,systemic lupus erythrematosus, Sjögren's syndrome or scleroderma (e.g.,systemic sceroderma).

In one example, the method comprises administering an effective amountof the immunoglobulin, such as a therapeutically effective amount of theimmunoglobulin, antibody or antigen binding fragment.

In one example, the method comprises administering between about 0.0001mg/kg and 50 mg/kg of immunoglobulin, antibody or antigen bindingfragment to the mammal. For example, the method comprises administeringbetween about 0.0005 mg/kg to about 40 mg/kg. For example, the methodcomprises administering between about 0.0005 mg/kg to about 30 mg/kg.For example, the method comprises administering between about 0.001mg/kg to about 20 mg/kg. For example, the method comprises administeringbetween about 0.001 mg/kg to about 10 mg/kg. For example, the methodcomprises administering between about 0.01 mg/kg to about 5 mg/kg. Forexample, the method comprises administering between about 0.001 mg/kg toabout 1 mg/kg.

In one example, the method comprises administering between about 0.1mg/kg to about 10 mg/kg of the immunoglobulin, antibody or antigenbinding fragment. For example, the method comprises administeringbetween about 0.1 mg/kg to about 5 mg/kg. For example, the methodcomprises administering between about 0.1 mg/kg to about 1 mg/kg.

In one example, the method comprises administering between about 10mg/kg to about 30 mg/kg of the immunoglobulin, antibody or antigenbinding fragment. For example, the method comprises administeringbetween about 20 mg/kg to about 30 mg/kg.

In one example, the immunoglobulin, antibody or antigen binding fragmentis administered at a dose of 0.01 mg/kg.

In one example, the immunoglobulin, antibody or antigen binding fragmentis administered at a dose of 0.1 mg/kg.

In one example, the immunoglobulin, antibody or antigen binding fragmentis administered at a dose of 1 mg/kg.

In one example, the immunoglobulin, antibody or antigen binding fragmentis administered at a dose of 10 mg/kg.

In one example, the immunoglobulin, antibody or antigen binding fragmentis administered at a dose of 30 mg/kg.

In one example, the immunoglobulin or antibody is administered to themammal a plurality of times. In one example, the period betweenadministrations is at least about 7 days, such as at least about 8 days,for example, at least about 9 days or 10 days. In one example, theperiod between administrations is at least about 11 days. In anotherexample, the period between administrations is at least about 15 days,such as at least about 16 days, for example, at least about 18 days or20 days. In one example, the period between administrations is at leastabout 22 days. In another example, the period between administrations isat least about 25 days, such as at least about 30 days, for example, atleast about 40 days or 45 days. In one example, the period betweenadministrations is at least about 57 or 60 days.

For example, the immunoglobulin, antibody or antigen binding domain isadministered at a dose of between 0.0001 mg/kg and 5 mg/kg, such asbetween 0.0005 mg/kg and 5 mg/kg, for example, between 0.001 mg/kg and 5mg/kg, and the period between administrations is at least about 7 daysor 8 days or 9 days or 10 days or 11 days or 14 days or 17 days or 21days or 22 days or 28 days or 29 days or 30 days or 1 calendar month.For example, the immunoglobulin, antibody or antigen binding domain isadministered at a dose of between 0.01 mg/kg and 5 mg/kg and the periodbetween administrations is at least about 7 days or 8 days or 9 days or10 days or 11 days or 14 days. For example, the immunoglobulin, antibodyor antigen binding domain is administered at a dose of between 0.01mg/kg and 2 mg/kg and the period between administrations is at leastabout 7 days or 8 days or 9 days or 10 days or 11 days or 14 days. Forexample, the immunoglobulin, antibody or antigen binding domain isadministered at a dose of between 0.01 mg/kg and 1 mg/kg and the periodbetween administrations is at least about 7 days or 8 days or 9 days or10 days or 11 days or 14 days. In some examples, the period betweenadministrations is at least about 7 days and less than about 22 days,such as at least about 11 days or IS days and less than about 20 days,for example at least about 13 days and less than about 18 days.

In one example, the immunoglobulin, antibody or antigen binding domainis administered at a dose of 0.01 mg/kg and the period betweenadministrations is 6 days or 7 days or 8 days or 9 days or 10 days or 11days or 14 days or 15 days.

In one example, the immunoglobulin, antibody or antigen binding domainis administered at a dose of 0.1 mg/kg and the period betweenadministrations is 6 days or 7 days or 8 days or 9 days or 10 days or 11days or 14 days or 15 days.

In one example, the immunoglobulin or antibody is administered at a doseof 1 mg/kg and the period between administrations is 6 days or 7 days or8 days or 9 days or 10 days or 11 days or 14 days or 15 days or 20 daysor 21 days or 22 days.

For example, the immunoglobulin or antibody is administered at a dose ofbetween 6 mg/kg and 50 mg/kg and the period between administrations isat least about 15 days. For example, the immunoglobulin or antibody isadministered at a dose of between 10 mg/kg and 30 mg/kg and the periodbetween administrations is at least about 14 or 15 days. For example,the immunoglobulin or antibody is administered at a dose of between 20mg/kg and 30 mg/kg and the period between administrations is at leastabout 14 or 15 days. In some examples, the period betweenadministrations is at least about 20 days and less than about 70 days,such as at least about 21 or 22 days and less than about 65 days, forexample at least about 25 days and less than about 57 days.

In one example, the immunoglobulin or antibody is administered at a doseof 10 mg/kg and the period between administrations is 14 days or 15 daysor 21 days or 22 days or 30 days or 48 days or 50 days or 56 days or 57days or 60 days.

In one example, the immunoglobulin or antibody is administered at a doseof 30 mg/kg and the period between administrations is 14 days or 15 daysor 21 days or 22 days or 30 days or 48 days or 50 days or 56 days or 57days or 60 days.

As discussed above, the inventor has found that following administrationof an immunoglobulin or antibody of the disclosure the number of NKcells is increased above the number present before administration withinabout 8 days. The inventor has also shown that increased numbers of NKcells increase the efficacy of an antibody or immunoglobulin of thedisclosure in inducing death of target cells. Thus, once the number ofNK cells is increased, a further dose of the antibody or immunoglobulincan be administered to induce a therapeutic/prophylactic effect. Forexample, an immunoglobulin, antibody or antigen binding fragment of thedisclosure is administered a plurality of times at a dose of betweenabout 0.001 mg/kg and about 1 mg/kg with a period betweenadministrations of at least about 7 days, such as, at least about 8days, for example, at least about 11 days, such as at least about 14days, for example, at least about 17 days, such as at least about 21days, for example, at least about 22 days, for example, 28 days or 29days or one calendar month or 56 or 57 or 60 days. In one example, theperiod between doses is about 7 days. In one example, the period betweendoses is about 8 days. In one example, the period between doses is about11 days. In one example, the period between doses is about 14 days. Inone example, the period between doses is about 17 days. In one example,the period between doses is about 21 days. In one example, the periodbetween doses is about 22 days. In one example, the period between dosesis about 28 days. In one example, the period between doses is about 29days. In one example, the dose is between about 0.01 mg/kg and about 0.1mg/kg, such as a dose of about 0.01 mg/kg or 0.1 mg/kg.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a graphical representation showing the number of NK cells ina sample from a non-human primate subject at various time points (asindicated) following administration of antibody CSL362X2. The number ofcells is represented as a percentage of the number of cells prior toadministering the antibody. Dosages of the antibody are indicated.

FIG. 1B is a graphical representation showing the number of NK cells ina sample from a non-human primate subject at various time points (asindicated) following administration of antibody CSL362B. The number ofcells is represented as a percentage of the number of cells prior toadministering the antibody. Dosages of the antibody are indicated.

FIG. 1C is a graphical representation showing the number of NK cells ina sample from a non-human primate subject at various time points (asindicated) following administration of a chimeric antibody (designatedCSL360) comprising a human IgG1 constant domain and the variable regionof antibody 7G3. The number of cells is represented as a percentage ofthe number of cells prior to administering the antibody. Dosages of theantibody are indicated.

FIG. 2A is a graphical representation showing the percentage of TF-1cells lysed in the presence of the indicated cell population andantibody CSL362X1 at various concentrations (as indicated on the Xaxis).

FIG. 2B is a graphical representation showing the percentage of AMLcells in the presence of various numbers of NK cells and antibodyCSL362X1. The ratio of effector cells (NK cells; E) to target cells(leukemia cells; T) is indicated on the X axis. Results generated suingcells from two patients are depicted.

DETAILED DESCRIPTION Key to Sequence Listing

SEQ ID NO: 1—amino acid sequence of II-3Rα chainSEQ ID NO: 2—amino acid sequence of LCDR1 of humanized anti-IL-3Rα chainantibody CSL362 and modified forms thereofSEQ ID NO: 3—amino acid sequence of LCDR2 of humanized anti-IL-3Rα chainantibody CSI362 and modified forms thereofSEQ ID NO: 4—amino acid sequence of LCDR3 of humanized anti-IL-3Rα chainantibody CSL362 and modified forms thereofSEQ ID NO: 5—amino acid sequence of HCDR1 of humanized anti-IL-3Rαchainantibody CSL362 and modified forms thereofSEQ ID NO: 6—amino acid sequence of HCDR2 of humanized anti-IL-3Rαchainantibody CSL362 and modified forms thereofSEQ ID NO: 7—amino acid sequence of HCDR3 of humanized anti-IL-3Rαchainantibody CSL362 and modified forms thereofSEQ ID NO: 8—amino acid sequence of light chain variable region ofhumanized anti-IL-3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 9—amino acid sequence of heavy chain variable region ofhumanized anti-IL-3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 10—amino acid sequence of heavy chain of humanizedanti-IL-3Rαchain antibody CSI362 and CSL362BSEQ ID NO: 11—amino acid sequence of heavy chain of humanizedanti-IL-3Rαchain antibody CSL362X1SEQ ID NO: 12—amino acid sequence of heavy chain of humanizedanti-IL-3Rαchain antibody CST362X2SEQ ID NO: 13—amino acid sequence of light chain of humanizedanti-IL-3Rαchain antibody CSL362 and modified forms thereofSEQ ID NO: 14—nucleotide sequence encoding a LCDR1 of humanizedanti-1-3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 15—nucleotide sequence encoding a LCDR2 of humanizedanti-IL-3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 16—nucleotide sequence encoding a LCDR3 of humanizedanti-IL-3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 17—nucleotide sequence encoding a HCDR1 of humanizedanti-IL3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 18—nucleotide sequence encoding a HCDR2 of humanizedanti-IL-3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 19—nucleotide sequence encoding a HCDR3 of humanizedanti-IL-3Rα chain antibody CSL362 and modified forms thereofSEQ ID NO: 20—nucleotide sequence encoding a light chain variable regionof humanized anti-IL-3Rα chain antibody CSL362 and modified formsthereofSEQ ID NO: 21—nucleotide sequence encoding a heavy chain variable regionof humanized anti-IL-3Rα chain antibody CSL362 and modified formsthereofSEQ ID NO: 22—nucleotide sequence encoding a heavy chain of humanizedanti-IL-3Rα chain antibody CSI362 and CS362B

SEQ ID NO: 23-nucleotide sequence encoding a light chain of humanizedanti-IL-3Rα chain antibody CSL362 and modified forms thereof.

General

Throughout this specification, unless specifically stated otherwise orthe context requires otherwise, reference to a single step, compositionof matter, group of steps or group of compositions of matter shall betaken to encompass one and a plurality (i.e. one or more) of thosesteps, compositions of matter, groups of steps or groups of compositionsof matter.

Those skilled in the art will appreciate that the present disclosure issusceptible to variations and modifications other than thosespecifically described. It is to be understood that the disclosureincludes all such variations and modifications. The disclosure alsoincludes all of the steps, features, compositions and compounds referredto or indicated in this specification, individually or collectively, andany and all combinations or any two or more of said steps or features.

The present disclosure is not to be limited in scope by the specificexamples described herein, which are intended for the purpose ofexemplification only. Functionally-equivalent products, compositions andmethods are clearly within the scope of the present disclosure.

Any example of the present disclosure herein shall be taken to applymutatis mutandis to any other example of the disclosure unlessspecifically stated otherwise.

Unless specifically defined otherwise, all technical and scientificterms used herein shall be taken to have the same meaning as commonlyunderstood by one of ordinary skill in the art (for example, in cellculture, molecular genetics, immunology, immunohistochemistry, proteinchemistry, and biochemistry).

Unless otherwise indicated, the recombinant protein, cell culture, andimmunological techniques utilized in the present disclosure are standardprocedures, well known to those skilled in the art. Such techniques aredescribed and explained throughout the literature in sources such as, J.Perbal, A Practical Guide to Molecular Cloning, John Wiley and Sons(1984), J. Sambrook et al. Molecular Cloning: A Laboratory Manual, ColdSpring Harbour Laboratory Press (1989), T. A. Brown (editor), EssentialMolecular Biology: A Practical Approach, Volumes 1 and 2, IRL Press(1991), D. M. Glover and B. D. Hlames (editors), DNA Cloning: APractical Approach, Volumes 1-4, IRL Press (1995 and 1996), and F. M.Ausubel et al. (editors), Current Protocols in Molecular Biology, GreenePub. Associates and Wiley-Interscience (1988, including all updatesuntil present), Ed Harlow and David Lane (editors) Antibodies: ALaboratory Manual, Cold Spring Harbour Iaboratory, (1988), and J. E.Coligan et al. (editors) Current Protocols in Immunology, John Wiley &Sons (including all updates until present).

The description and definitions of variable regions and parts thereof,immunoglobulins, antibodies and fragments thereof herein may be furtherclarified by the discussion in Kabat Sequences of Proteins ofImmunological Interest, National Institutes of Health, Bethesda, Md.,1987 and 1991.

The term “and/or”, e.g., “X and/or Y” shall be understood to mean either“X and Y” or “X or Y” and shall be taken to provide explicit support forboth meanings or for either meaning.

Throughout this specification the word “comprise”, or variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated element, integer or step, or group of elements, integers orsteps, but not the exclusion of any other element, integer or step, orgroup of elements, integers or steps.

As used herein the term “derived from” shall be taken to indicate that aspecified integer may be obtained from a particular source albeit notnecessarily directly from that source.

Selected Definitions

As used herein, the term “immunoglobulin” includes any antigen-bindingprotein product of the immunoglobulin gene complex, includingimmunoglobulin isotypes IgA, IgD, IgM, IgG and IgE and antigen-bindingfragments thereof. Exemplary immunoglobulins are antibodies. Exemplaryimmunoglobulins are monoclonal. Included in the term “immunoglobulin”are any immunoglobulins that are appropriately de-immunized to therebyreduce or eliminate an immune response by a mammal to an immunoglobulinthat has been administered to the mammal. In the case of treatment ofhumans, suitable immunoglobulins include chimeric, humanized or humanimmunoglobulins. Also included within the term “immunoglobulin” aremodified, mutagenized, chimeric and/or humanized immunoglobulins thatcomprise altered or variant amino acid residues, sequences orglycosylation, whether naturally occurring or produced by humanintervention (e.g. by recombinant DNA technology). Exemplary proteinsinclude an Fc receptor binding portion. For example, proteinsencompassed by the term “immunoglobulin” include domain antibodies,camelid antibodies and antibodies from cartilaginous fish (i.e.,immunoglobulin new antigen receptors (IgNARs)). Generally, camelidantibodies and IgNARs comprise a V_(H), however lack a V_(L) and areoften referred to as heavy chain immunoglobulins. Other“immunoglobulins” include T cell receptors and other immunoglobulin-likedomain containing proteins that are capable of binding to an antigen,e.g., by virtue of an antigen binding site comprising a variable region.

The skilled artisan will be aware that an “antibody” is generallyconsidered to be a protein that comprises a variable region made up of aplurality of polypeptide chains, e.g., a polypeptide comprising a V_(L)and a polypeptide comprising a V_(H). An antibody also generallycomprises constant domains, some of which can be arranged into aconstant region or constant fragment or fragment crystallizable (Fc). AV_(H) and a V_(L) interact to form a Fv comprising an antigen bindingregion that is capable of specifically binding to one or a few closelyrelated antigens. Generally, a light chain from mammals is either a κlight chain or a λ light chain and a heavy chain from mammals is α, δ,ε, γ, or μ. Antibodies can be of any type (e.g., IgG, IgF, IgM, IgD,IgA, and IgY), class (e.g., IgG₁, IgG₂, IgG₃, IgG₄, IgA₁ and IgA₂) orsubclass. The term “antibody” encompasses humanized antibodies.

The term “humanized antibody” shall be understood to refer to anantibody comprising a human-like variable region including CDRs from anantibody from a non-human species (e.g., mouse) grafted onto or insertedinto FRs from a human antibody (this type of antibody is also referredto a “CDR-grafted antibody”). Humanized antibodies also includeantibodies in which one or more residues of the human antibody aremodified by one or more amino acid substitutions and/or one or more FRresidues of the human protein are replaced by corresponding non-humanresidues. As exemplified herein, humanized antibodies may also compriseresidues which are found in neither the human antibody or in thenon-human antibody. Any additional regions of the antibody (e.g., Fcregion) are generally human. Humanization can be performed using amethod known in the art, e.g., U.S. Pat. No. 5,225,539, U.S. Pat. No.6,054,297, U.S. Pat. No. 7,566,771 or U.S. Pat. No. 5,585,089. The term“humanized antibody” also encompasses a super-humanized protein, e.g.,as described in U.S. Pat. No. 7,732,578.

The terms “full-length antibody”, “intact antibody” or “whole antibody”are used interchangeably to refer to an antibody in its substantiallyintact form, as opposed to an antigen binding fragment of an antibody.Specifically, whole antibodies include those with heavy and light chainsincluding an Fc region. The constant domains may be wild-type sequenceconstant domains (e.g., human wild-type sequence constant domains) oramino acid sequence variants thereof. In some cases, the intact antibodymay be capable of inducing one or more effector functions.

The term “naked antibody” refers to an antibody that is not conjugatedto another compound, e.g., a toxic compound or radiolabel.

An “antigen binding fragment” of an antibody comprises the antigenbinding domain and/or the variable region of the intact antibody.Examples of antibody fragments include Fab, Fab′, F(ab′)₂ and Fvfragments; diabodies; linear antibodies; single-chain antibody moleculesand multispecific antibodies formed from antibody fragments.

In the context of the present disclosure, “effector functions” refer tothose biological activities mediated by cells or proteins that bind tothe Fc region (a native sequence Fc region or amino acid sequencevariant Fc region) of an antibody that result in killing of a cell.Examples of effector functions induced by antibodies or immunoglobulinsinclude: complement dependent cytotoxicity,antibody-dependent-cell-mediated cytotoxicity (ADCC);antibody-dependent-cell-phagocytosis (ADCP); and B-cell activation. Inthe context of the present disclosure, the term or “effector functioninduced by an antibody” or like term is used interchangeably with“effector function of an immunoglobulin” or “effector function of anantibody” or like team and each provides literal support for the other.

“Antibody-dependent-cell-mediated cytotoxicity” or “ADCC” refers to aform of cytotoxicity in which secreted Ig bound onto Fc receptors(“FcRs”) present on certain cytotoxic cells (e.g., natural killer (“NK”)cells, neutrophils and macrophages) enable these cytotoxic effectorcells to bind specifically to an antigen-bearing target-cell andsubsequently kill the target-cell with cytotoxins. To assess ADCCactivity of a molecule of interest, an in vitro ADCC assay may beperformed. Useful effector cells for such assays include peripheralblood mononuclear cells (“PBMC”) and NK cells.

As used herein, “variable region” refers to the portions of the lightand/or heavy chains of an antibody as defined herein that is capable ofspecifically binding to an antigen and, for example, includes amino acidsequences of CDRs; i.e., CDR1, CDR2, and CDR3, and framework regions(FRs). For example, the variable region comprises three or four FRs(e.g., FR1, FR2, FR3 and optionally FR4) together with three CDRs. V_(H)refers to the variable region of the heavy chain. V_(L) refers to thevariable region of the light chain.

As used herein, the term “complementarity determining regions” (syn.CDRs; i.e., CDR1, CDR2, and CDR3) refers to the amino acid residues ofan antibody variable region the presence of which are major contributorsto specific antigen binding. Each variable region typically has threeCDR regions identified as CDR1, CDR2 and CDR3. In one example, the aminoacid positions assigned to CDRs and FRs are defined according to KabatSequences of Proteins of Immunological Interet, National Institutes ofHealth, Bethesda, Md., 1987 and 1991 (also referred to herein as “theKabat numbering system”. According to the numbering system of Kabat,V_(H) FRs and CDRs are positioned as follows: residues 1-30 (FR1), 31-35(CDR1), 36-49 (FR2), 50-65 (CDR2), 66-94 (FR3), 95-102 (CDR3) and103-113 (FR4). According to the numbering system of Kabat, V_(L) FRs andCDRs are positioned as follows: residues 1-23 (FR1), 24-34 (CDR1), 35-49(FR2), 50-56 (CDR2), 57-88 (FR3), 89-97 (CDR3) and 98-107 (PR4).

“Framework regions” (hereinafter FR) are those variable domain residuesother than the CDR residues.

The term “constant region” as used herein, refers to a portion of heavychain or light chain of an antibody other than the variable region. In aheavy chain, the constant region generally comprises a plurality ofconstant domains and a hinge region, e.g., a IgG constant regioncomprises the following linked components, a constant heavy (C_(H))1, alinker, a C_(H)2 and a C_(H)3. In a heavy chain, a constant regioncomprises a Fc. In a light chain, a constant region generally compriseone constant domain (a C_(I)1).

The term “fragment crystallizable” or “Fc” or “Fc region” or “Fcportion” (which can be used interchangeably herein) refers to a regionof an antibody comprising at least one constant domain and which isgenerally (though not necessarily) glycosylated and which is capable ofbinding to one or more Fc receptors and/or components of the complementcascade. The heavy chain constant region can be selected from any of thefive isotypes: α, δ, ε, γ, or μ. Furthermore, heavy chains of varioussubclasses (such as the IgG subclasses of heavy chains) are responsiblefor different effector functions and thus, by choosing the desired heavychain constant region, proteins with desired effector function can beproduced. Exemplary heavy chain constant regions are gamma 1 (IgG1),gamma 2 (IgG2) and gamma 3 (IgG3), or hybrids thereof.

A “constant domain” is a domain in an antibody the sequence of which ishighly similar in antibodies/antibodies of the same type, e.g., IgG orIgM or IgE. A constant region of an antibody generally comprises aplurality of constant domains, e.g., the constant region of γ, α or δheavy chain comprises two constant domains.

As used herein, the term “specifically binds” shall be taken to mean animmunoglobulin or antibody by which is meant that the bindinginteraction between an immunoglobulin or antibody and IL-3Rα chain isdependent on the presence of the antigenic determinant or epitope of anIL-3Rα chain bound by the immunoglobulin or antibody. Accordingly, theimmunoglobulin or antibody preferentially binds or recognizes an IL-3Rαchain antigenic determinant or epitope even when present in a mixture ofother molecules or organisms. In one example, the immunoglobulin orantibody reacts or associates more frequently, more rapidly, withgreater duration and/or with greater affinity with IL-3Rα or cellexpressing same than it does with alternative antigens or cells. It isalso understood by reading this definition that, for example, animmunoglobulin or antibody specifically binds to IL-3Rα may or may notspecifically bind to a second antigen. As such, “specific binding” doesnot necessarily require exclusive binding or non-detectable binding ofanother antigen. The term “specifically binds” is used interchangeablywith “selectively binds” herein. Generally, reference herein to bindingmeans specific binding, and each term shall be understood to provideexplicit support for the other term. “In one example, “specific binding”to with IL-3Rα or cell expressing same, means that the immunoglobulin orantibody binds to the with IL-3Rα or cell expressing same with anequilibrium constant (K) of 100 nM or less, such as 50 nM or less, forexample 20 nM or less, such as, 1 nM or less, e.g., 0.8 nM or less.

The term “EU numbering system of Kabat” will be understood to mean thenumbering of an antibody heavy chain is according to the EU index astaught in Kabat et al., 1991, Sequences of Proteins of ImmunologicalInterest, 5th Ed., United States Public Health Service, NationalInstitutes of Health, Bethesda. The EU index is based on the residuenumbering of the human IgG EU antibody.

As used herein, the term “II-3Rα-mediated condition” will be understoodto mean a condition associated with or caused by excessive IL-3Rαexpression and/or an excessive number of IL-3Rα expressing cells in amammal, such as cancer cells (e.g., leukemic cells) and/or immune cells(e.g., plasmacytoid dendritic cells).

As used herein, the term “myelodysplastic syndrome” or “MDS” will beunderstood to refer to a diverse collection of hematological medicalconditions that involve ineffective production (or dysplasia) of themyeloid class of blood cells. Subjects with MDS often develop severeanemia and can require frequent blood transfusions. In many cases, asMDS progresses the subject develops cytopenias (low blood counts) due toprogressive bone marrow failure. In about one third of patients withMDS, the disease transforms into acute myelogenous leukemia (AML). TheMDS can be diagnosed or classified to various systems, including theFrench-American-British Classification System (Bennett et al., Br. J.Haematol. 33: 451-458, 1976), The International Prognostic ScoringSystem (Greenberg et al., Blood 89: 2079-88, 1997) or a system publishedby the World Health Organization.

As used herein, the term “treatment” refers to clinical interventiondesigned to alter the natural course of the individual or cell beingtreated during the course of clinical pathology. Desirable effects oftreatment include decreasing the rate of disease progression,ameliorating or palliating the disease state, and remission or improvedprognosis. An individual is successfully “treated”, for example, if oneor more symptoms associated with a disease are mitigated or eliminated.

As used herein, the term “prevention” includes providing prophylaxiswith respect to occurrence or recurrence of a disease in an individual.An individual may be predisposed to or at risk of developing the diseaseor disease relapse but has not yet been diagnosed with the disease orthe relapse.

As used herein, a mammal “at risk” of developing a disease or conditionor relapse thereof or relapsing may or may not have detectable diseaseor symptoms of disease, and may or may not have displayed detectabledisease or symptoms of disease prior to the treatment according to thepresent disclosure. “At risk” denotes that a mammal has one or more riskfactors, which are measurable parameters that correlate with developmentof the disease or condition, as known in the art and/or describedherein.

An “effective amount” refers to at least an amount effective, at dosagesand for periods of time necessary, to achieve the desired therapeutic orprophylactic result. An effective amount can be provided in one or moreadministrations. In some examples of the present disclosure, the term“effective amount” is meant an amount necessary to effect treatment of adisease or condition as hereinbefore described. The effective amount mayvary according to the disease or condition to be treated and alsoaccording to the weight, age, racial background, sex, health and/orphysical condition and other factors relevant to the mammal beingtreated. Typically, the effective amount will fall within a relativelybroad range (e.g. a “dosage” range) that can be determined throughroutine trial and experimentation by a medical practitioner. Theeffective amount can be administered in a single dose or in a doserepeated once or several times over a treatment period.

A “therapeutically effective amount” is at least the minimumconcentration required to effect a measurable improvement of aparticular disorder (e.g., SLE). A therapeutically effective amountherein may vary according to factors such as the disease state, age,sex, and weight of the patient, and the ability of the immunoglobulin orantibody to elicit a desired response in the individual. Atherapeutically effective amount is also one in which any toxic ordetrimental effects of the immunoglobulin or antibody are outweighed bythe therapeutically beneficial effects.

A “prophylactically effective amount” refers to an amount effective, atthe dosages and for periods of time necessary, to achieve the desiredprophylactic result. Typically but not necessarily, since a prophylacticdose is used in mammals prior to or at an earlier stage of disease, aprophylactically effective amount may be less than a therapeuticallyeffective amount.

Reference herein to “the number of NK cells in the mammal” will beunderstood to include the number of NK cells in a sample from a mammaland not to require determining the total number of NK cells in a mammal.This number can be expressed as, for example, cells per mL or dL or as apercentage of the number of cells from a sample taken at a differentpoint in time from the mammal.

For the purposes of nomenclature only and not limitation, the amino acidsequence of an IL-3Rα chain is taught in Gene ID Accession Number 3563and/or in SEQ ID NO: 1.

The “mammal” treated according to the present disclosure may be amammal, such as a non-human primate or a human. In one example, themammal is a human.

The term “sequence identity” is used herein in its broadest sense toinclude the number of exact nucleotide or amino acid matches havingregard to an appropriate alignment using a standard algorithm, havingregard to the extent that sequences are identical over a window ofcomparison. Sequence identity may be determined by alignment of comparedsequences using computerised implementations of algorithms (Geneworksprogram by Intelligenetics; GAP, BESTFIT, FASTA, and TFASTA in theWisconsin Genetics Software Package Release 7.0, Genetics ComputerGroup, 575 Science Drive Madison, Wis., USA, incorporated herein byreference) or by inspection and the best alignment (i.e., resulting inthe highest percentage homology over the comparison window) generated byany of the various methods selected. Reference also may be made to theBLAST family of programs as for example disclosed by Altschul et al.,1997, Nucl. Acids Res. 25 3389. A detailed discussion of sequenceanalysis can be found in Unit 19.3 of CURRENT PROTOCOLS IN MOLECULARBIOLOGY Eds. Ausubel et al. (John Wiley & Sons Inc NY, 1995-1999).

The disclosure also provides derivatives of anti-IL-3Rα immunoglobulins,antibodies or antigen binding fragments of the disclosure. As usedherein, “derivative” proteins have been altered, for example bypost-translational modification (e.g phosphorylation, acetylation etc),modification of glycosylation (e.g. adding, removing or alteringglycosylation) and/or inclusion of additional amino acid sequences aswould be understood in the art.

The term “nucleic acid” as used herein designates single- ordouble-stranded DNA and RNA capable of encoding an immunoglobulin,antibody or antigen binding fragment of the disclosure or a polypeptidecomponent thereof. DNA includes genomic DNA and cDNA. RNA includes mRNAand cRNA. Nucleic acids may also be DNA-RNA hybrids. A nucleic acidcomprises a nucleotide sequence which typically includes nucleotidesthat comprise an A, G, C, T or U base. However, nucleotide sequences mayinclude other bases such as inosine, methylycytosine, methylinosine,methyladenosine and/or thiouridine, although without limitation thereto.

“Hybridize and Hybridization” is used herein to denote the pairing of atleast partly complementary nucleotide sequences to produce a DNA-DNA,RNA-RNA or DNA-RNA hybrid. Hybrid sequences comprising complementarynucleotide sequences occur through base-pairing between complementarypurines and pyrimidines as are well known in the art.

In this regard, it will be appreciated that modified purines (forexample, inosine, methylinosine and methyladenosine) and modifiedpyrimidines (thiouridine and methylcytosine) may also engage in basepairing.

“Stringency” as used herein, refers to temperature and ionic strengthconditions, and presence or absence of certain organic solvents and/ordetergents during hybridisation. The higher the stringency, the higherwill be the required level of complementarity between hybridizingnucleotide sequences.

“High stringency conditions” designates those conditions under whichonly nucleic acid having a high frequency of complementary bases willhybridize.

Reference herein to high stringency conditions include and encompass:—

-   -   (i) from at least about 31% v/v to at least about 50% v/v        formamide and from at least about 0.01 M to at least about 0.15        M salt for hybridisation at 42° C., and at least about 0.01 M to        at least about 0.15 M salt for washing at 42° C.;    -   (ii) 1% BSA, 1 mM EDTA, 0.5 M NaHPO₄ (pH 7.2), 7% SDS for        hybridization at 65° C., and (a) 0.1×SSC, 0.1% SDS; or (b) 0.5%        BSA, 1 mM EDTA, 40 mM NaHPO₄ (pH 7.2), 1% SDS for washing at a        temperature in excess of 65° C. for about one hour; and    -   (iii) 0.2×SSC, 0.1% SDS for washing at or above 68° C. for about        20 minutes.

In general, washing is carried out at T_(m)=69.3+0.41 (G+C) %−12° C. Ingeneral, the T_(m) of a duplex DNA decreases by about 1° C. with everyincrease of 1% in the number of mismatched bases.

Notwithstanding the above, stringent conditions are known in the art,such as described in Chapters 2.9 and 2.10 of. Ausubel et al., CURRENTPROTOCOLS IN MOLECULAR BIOLOGY John Wiley & Sons, Inc. 1995-2009

An “expression vector” may be either a self-replicatingextra-chromosomal vector such as a plasmid, or a vector that integratesinto a host genome.

Immunoglobulins

Suitably, an immunoglobulin or antibody of the disclosure selectivelybinds IL-3Rα chain, by which is meant that the binding interactionbetween the immunoglobulin or antibody and IL-3Rα chain is dependent onthe presence of the antigenic determinant or epitope of an IL-3Rα chainbound by the immunoglobulin. Accordingly, the immunoglobulin or antibodypreferentially binds or recognizes an IL-3Rα chain antigenic determinantor epitope even when present in a mixture of other molecules ororganisms.

Antibodies

In one example, an immunoglobulin as described herein according to anyexample is an antibody, e.g., comprising CDRs and/or one or morevariable regions described herein.

Suitably, the immunoglobulin is a humanized, chimeric or human antibodythat comprises light and heavy chain CDR 1, 2 and 3 amino acid sequencesaccording to SEQ ID NOs: 2-7 respectively. In one example, the antibodycomprise a heavy chain variable region amino acid sequence according toSEQ ID NO: 9 and a light chain variable region amino acid sequenceaccording to SEQ ID NO: 8. In one example, the antibody comprises aheavy chain amino acid sequence according to SEQ ID NO: 10, SEQ ID NO:11 or SEQ ID NO: 12 and a light chain amino acid sequence according toSEQ ID NO: 13.

In one example, the antibody is a recombinant antibody. Methods forproducing antibodies comprising CDRs and/or variable regions describedherein will be apparent to the skilled artisan based on the disclosureherein and/or documents referred to herein.

In one example, an antibody of the disclosure comprises a V_(H) and/or aV_(L) comprising CDRs as set forth herein and FRs from a human antibody.Optionally, the FRs comprise one or more amino acid substitutions, e.g.,2 or more or 3 or more or 4 or more of 5 or more or 10 or more or IS ormore. In one example, the FRs comprise no more than 30 amino acidsubstitutions, e.g., no more than 20 amino acid substitutions comparedto the human FRs.

In one example, an antibody of the disclosure comprises a V_(H) and/or aV_(L) comprising CDRs as set forth herein and FRs from a non-humanprimate antibody, i.e., the antibody is Synhumanized, e.g., as describedin WO2007/019620.

In one example, an antibody of the disclosure is a composite antibody,e.g., as described in WO2006/082406.

One exemplary antibody of the disclosure is a humanized antibody, e.g.,as defined herein. Exemplary humanized antibodies are described herein.In one example, the humanized antibody has been affinity matured. In oneexample, the humanized antibody comprises:

(i) a Vt comprising:

a) a CDR1 comprising a sequence set forth in SEQ ID NO: 2 (or encoded bya sequence set forth in SEQ ID NO: 14);

b) a CDR2 comprising a sequence set forth in SEQ ID NO: 3 (or encoded bya sequence set forth in SEQ ID NO: 15); and

c) a CDR3 comprising a sequence set forth in SEQ ID NO: 4 (or encoded bya sequence set forth in SEQ ID NO: 16); and

(ii) a V comprising:

d) a CDR1 comprising a sequence set forth in SEQ ID NO: 5 (or encoded bya sequence set forth in SEQ ID NO: 17);

e) a CDR2 comprising a sequence set forth in SEQ ID NO: 6 (or encoded bya sequence set forth in SEQ UD NO: 18); and

f) a CDR3 comprising a sequence set forth in SEQ ID NO: 7 (or encoded bya sequence set forth in SEQ ID NO: 19).

Those skilled in the art will appreciate that immunoglobulins orantibodies of the disclosure may include modifications that introducesequences not naturally found in humans, for example to increaseaffinity or effector function.

The disclosure also provides variants of the immunoglobulin or antibodyof the disclosure. Suitably, variants have at least 80%, 85%, 90%, 91%,92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity with any ofthe amino acid sequences set forth in SEQ ID NOS:2-13.

For example, it is understood in the art that some amino acids may besubstituted or deleted without adversely or significantly affecting theIL-3Rαspecificity and/or effector function of the immunoglobulin orantibody (e.g. conservative substitutions).

Derivatives of antibodies or immununoglobulins contemplated by thedisclosure include, but are not limited to, modification to amino acidside chains, incorporation of unnatural amino acids and/or theirderivatives during peptide or polypeptide synthesis and the use ofcrosslinkers.

Exemplary antibodies and antigen binding fragments thereof of thepresent disclosure are described in Table 1.

TABLE 1 Exemplary antibodies and antigen binding fragments thereof NameHeavy Chain SEQ ID NO: Light Chain SEQ ID NO: CSL362 Fv   9¹   8¹ CSL36210 13 CSL362B  10² 13 CSL362X1 11 13 CSL362X2 12 13 ¹Variable regionsequence only. ²Heavy chain constant region is afucosylated.

Antibody Fragments Single-Domain Antibodies

In some examples, an antigen binding fragment of an antibody of thedisclosure is or comprises a single-domain antibody (which is usedinterchangeably with the term “domain antibody” or “dAb”). Asingle-domain antibody is a single polypeptide chain comprising all or aportion of the heavy chain variable domain of an antibody.

Diabodies, Triabodies, Tetrabodies

In some examples, an antigen binding fragment of the disclosure is orcomprises a diabody, triabody, tetrabody or higher order protein complexsuch as those described in WO98/044001 and/or WO94/007921.

For example, a diabody is a protein comprising two associatedpolypeptide chains, each polypeptide chain comprising the structureV_(L)-X-V_(H) or V_(H)-X-V_(L), wherein X is a linker comprisinginsufficient residues to permit the V_(H) and V_(L) in a singlepolypeptide chain to associate (or form an Fv) or is absent, and whereinthe V_(H) of one polypeptide chain binds to a V_(L) of the otherpolypeptide chain to form an antigen binding site, i.e., to form a Fvmolecule capable of specifically binding to one or more antigens. TheV_(L) and V_(H) can be the same in each polypeptide chain or the V_(L)and V_(H) can be different in each polypeptide chain so as to form abispecific diabody (i.e., comprising two Fvs having differentspecificity).

A diabody, triabody, tetrabody, etc capable of inducing effectoractivity can be produced using an antigen binding domain capable ofbinding to IL-3Rα and an antigen binding domain capable of binding to acell surface molecule on an immune cell, e.g., a T cell (e.g., CD3).

Single Chain Fv (scFv) Fragments

The skilled artisan will be aware that scFvs comprise V_(H) and V_(L)regions in a single polypeptide chain and a polypeptide linker betweenthe V_(H) and V_(L) which enables the scFv to form the desired structurefor antigen binding (i.e, for the V_(H) and V_(L) of the singlepolypeptide chain to associate with one another to form a Fv). Forexample, the linker comprises in excess of 12 amino acid residues with(Gly₄Ser)₃ being one of the more favored linkers for a scFv.

The present disclosure also contemplates a disulfide stabilized Fv (ordiFv or dsFv), in which a single cysteine residue is introduced into aFR of V_(H) and a FR of V_(L) and the cysteine residues linked by adisulfide bond to yield a stable Fv.

Alternatively, or in addition, the present disclosure encompasses adimeric scFv, i.e., a protein comprising two scFv molecules linked by anon-covalent or covalent linkage, e.g., by a leucine zipper domain(e.g., derived from Fos or Jun). Alternatively, two scFvs are linked bya peptide linker of sufficient length to permit both scFvs to form andto bind to an antigen, e.g., as described in US20060263367.

The present disclosure also contemplates a dimeric scFv capable ofinducing effector activity. For example, one scFv binds to IL-3Rα andcomprises CDRs and/or variable regions described herein and another scFvbinds to a cell surface molecule on an immune cell, e.g., a T cell(e.g., CD3 or CD19). In one example, the dimeric protein is acombination of a dAb and a scFv. Examples of bispecific antibodyfragments capable of inducing effector function are described, forexample, in U.S. Pat. No. 7,235,641.

Other Antibodies and Antibody Fragments

The present disclosure also contemplates other antibodies and antibodyfragments, such as:

(i) “key and hole” bispecific proteins as described in U.S. Pat. No.5,731,168;(ii) heteroconjugate proteins, e.g., as described in U.S. Pat. No.4,676,980;(iii) heteroconjugate proteins produced using a chemical cross-linker,e.g., as described in U.S. Pat. No. 4,676,980; and(iv) Fab₃ (e.g., as described in EP19930302894).

Constant Regions

The present disclosure encompasses immunoglobulins and antibodies andantigen binding fragments comprising a constant region of an antibodyand/or a Fc region of an antibody.

Sequences of constant regions and/or Fc regions useful for producing theimmunoglobulins, antibodies or antigen binding fragments of the presentdisclosure may be obtained from a number of different sources. In someexamples, the constant region, Fc or portion thereof of theimmunoglobulin, antibody or antigen binding fragment is derived from ahuman antibody. The constant region, Fc or portion thereof may bederived from any antibody class, including IgA, IgM, IgG, IgD, IgA andIgE, and any antibody isotype, including IgG1, IgG2, IgG3 and IgG4. Inone example, the constant region or Fc is human isotype IgG1 or humanisotype IgG2 or human isotype IgG3 or a hybrid of any of the foregoing.

In one example, the constant region or Fc region is capable of inducingan effector function. For example, the constant region or Fc region is ahuman IgG1 or IgG3 Fc region. In another example, the constant region orFc region is a hybrid of an IgG1 and an IgG2 constant region or Fcregion or a hybrid of an IgG1 and an IgG3 constant region or Fc regionor a hybrid of an IgG2 and an IgG3 constant region or Fc region.Exemplary hybrids of human IgG1 and IgG2 constant region or Pc regionsare described in Chappel et al., Proc. Nad Acad. Sci. USA, 88:9036-9040, 1991.

Methods for determining whether or not a Fc region can induce effectorfunction will be apparent to the skilled artisan and/or describedherein.

Effector Function

Suitably, an anti-IL-3Rα immunoglobulin, antibody or antigen bindingfragment of the disclosure has or displays an effector function thatfacilitates or enables at least partial depletion, substantial depletionor elimination of IL-3Rα cells. Such an effector function may beenhanced binding affinity to Fc receptors, antibody-dependentcell-mediated cytotoxicity (ADCC), antibody-dependent cell mediatedphagocytosis (ADCP) and/or complement dependent cytotoxicity (CDC).

As will be apparent to the skilled artisan based on the descriptionherein, some examples of the present disclosure include animmunoglobulin, antibody or antigen binding fragment capable of inducingeffector function.

For the IgG class of antibodies, these effector functions are governedby engagement of the Pc region with a family of receptors referred to asthe Foy receptors (FcγRs) which are expressed on a variety of immunecells and/or with complement, e.g., Clq. Formation of the Fc/FcγRcomplex recruits these cells to sites of bound antigen, typicallyresulting in signaling and subsequent immune responses. Methods foroptimizing the binding affinity of the FcγRs to the antibody Fc regionin order to enhance the effector functions, in particular to alter theADCC and/or CDC activity relative to the “parent” Fc region, are knownto persons skilled in the art. These methods can include modification ofthe Fc region of the antibody to enhance its interaction with relevantFc receptors and increase its potential to facilitate ADCC and ADCP.Enhancements in ADCC activity have also been described following themodification of the oligosaccharide covalently attached to IgG1antibodies at the conserved Asn297 in the Fc region.

In this regard, it will be appreciated that in some non-limitingexamples, enhancing effector function such as ADCC may be achieved bymodification of an immunoglobulin or antibody which has a normallyglycosylated wild-type constant domain, including alteration or removalof glycosylation (see for example WO00/61739) and/or amino acid sequencemutations (see for example WO2008036688).

In one example, the immunoglobulin, antibody or antigen binding fragmentbinds to IL-3Rα in such a manner that it is capable of inducing aneffector function, such as, ADCC.

In one example, the immunoglobulin, antibody or antigen binding fragmentbinds to an epitope within IL3Rα that permits it to induce an effectorfunction, such as ADCC.

In another example, the immunoglobulin, antibody or antigen bindingfragment is capable of binding to IL-3Rα on a cell in a mammal tothereby induce an effector function, such as ADCC.

For example, the immunoglobulin, antibody or antigen binding fragmentremains bound to IL-3Rα on the surface of a cell for a time sufficientto induce an effector function, such as ADCC. For example, theimmunoglobulin or antibody is not internalized too quickly to permitADCC to be induced.

Alternatively, or in addition, the immunoglobulin, antibody or antigenbinding fragment is bound to the IL-3Rα on the surface of the cell in amanner permitting an immune effector cell to bind to a constant regionor Fc region in the immunoglobulin, antibody or antigen binding fragmentand induce an effector function, such as ADCC. For example, the Fcregion of the immunoglobulin, antibody or antigen binding fragment isexposed in such a manner when the immunoglobulin, antibody or antigenbinding fragment is bound to the IL-3Rα that is capable of interactingwith a Fc receptor (e.g., a FcγR) on an immune effector cell. In thecontext of the present disclosure, the term “immune effector cell” shallbe understood to mean any cell that expresses a Fe receptor and that iscapable of killing a cell to which it is bound by ADCC or ADCP. In oneexample, the immune effector cell is a NK cell.

Each of the above paragraphs relating to effector functions of animmunoglobulin, antibody or antigen binding fragment shall be taken toapply mutatis mutandis to inducing CDC. For example, the immunoglobulin,antibody or antigen binding fragment is bound to the IL-3Rα on thesurface of the cell in a manner permitting complement component Clq tobind to a constant region or Fc region in the immunoglobulin, antibodyor antigen binding fragment and induce CDC.

In one example, the immunoglobulin, antibody or antigen binding fragmentis capable of inducing an enhanced level of effector function.

In one example, the level of effector function induced by the constantregion or Fc region is enhanced relative to a wild-type constant regionor Fc region of an IgG1 antibody or a wild-type constant region or Fcregion of an IgG3 antibody.

In another example, the constant region or Fc region is modified toincrease the level of effector function it is capable of inducingcompared to the constant region or Fc region without the modification.Such modifications can be at the amino acid level and/or the secondarystructural level and/or the tertiary structural level and/or to theglycosylation of the constant region or Fc region.

The skilled addressee will appreciate that greater effector function maybe manifested in any of a number of ways, for example as a greater levelof effect, a more sustained effect or a faster rate of effect.

For example, the anti-IL-3Rα immunoglobulin, antibody or antigen bindingfragment has or displays an effector function that includesantibody-dependent cell-mediated cytotoxicity (ADCC).

In one example, the constant region or Pc region comprises one or moreamino acid modifications that increase its ability to induce enhancedeffector function. In one example, the constant region or Fc regionbinds with greater affinity to one or more FcγRs. In one example, theconstant region or Fc region has an affinity for an FcγR that is morethan 1-fold greater than that of a wild-type constant region or Fcregion or more than 5-fold greater than that of a wild-type constantregion or Fc region or between 5-fold and 300-fold greater than that ofa wild-type constant region or Fc region. In one example, the constantregion or Fc region comprises at least one amino acid substitution at aposition selected from the group consisting of: 230, 233, 234, 235, 239,240, 243, 264, 266, 272, 274, 275, 276, 278, 302, 318, 324, 325, 326,328, 330, 332, and 335, numbered according to the EU index of Kabat. Inone example, the constant region or Fc region comprise at least oneamino acid substitution selected from the group consisting of: P230A,E233D, L234E, L234Y, L2341, L235D, L235S, L235Y, L235I, S239D, S239E,S239N, S239Q, S239T, V240I, V240M, F243L, V264I, V264T, V264Y, V2661,F272Y, K274T, K274E, K274R, K274L, K274Y, F275W, N276L, Y278T, V3021,E318R, S324D, S3241, S324V, N325T, K326I, K326T, L328M, L3281, L328Q,L328D, L328V, L328T, A330Y, A330L, A330I, I332D, I332E, I332N, I332Q,T335D, T335R, and T335Y, numbered according to the EU index of Kabat. Inone example, the constant region or Fc region comprises amino acidsubstitutions selected from the group consisting of V264I, F243L/V2641,L328M, I332E, L328M/I332E, V264I/I332E, S298A/I332E, S239E/I332E,S239Q/I332E, S239, A330Y, 1332D, L328I/I332E, L328Q/I332E, V264T, V240I,V266I, S239D, S239D/I332D, S239D/I332E, S239D/I332N, S239D/I332Q,S239E/I332D, S239E/I332N, S239E/I332Q, S239N/I332D, S239N/332F,S239Q/I332D, A330Y/I332E, V2641/A330Y/I332E, A330L/I332E,V264I/A330L/A332E, L234E, L234Y, L2341, 1235D, L235S, 1235Y, L2351,S239T, V240M, V264Y, A3301, N325T, L328D/I332E, L328V/I332E,L328T/I332E, L328I/I332E, S239FV264I/I332E, S239Q/V264I/I332E,S239E/V264/A330Y/I332E, S239D/A330Y/I332F, S239N/A330Y/I332E,S239D/A330L/I332E, S239N/A330L/I332E, V2641/S298A/I332E,S239D/S298A/I332E, S239N/S298A/I332E, S239D/V264I/I332E,S239D/V264/S298A/I332E, S239D/V264I/A330L/I332E, S239D/I332E/A3301,P230A, P230A/E233D/I332E, E272Y, K274T, K274E, K274R, K274L, K274Y,F275W, N276L, Y278T, V3021, E318R, S324D, S3241, S324V, K326I, K326T,T335D, T335R, T335Y, V2401/V266I, S239D/A330Y/I332E/L234I,S239D/A330Y/I332E/L23SD, S239D/A330Y/I332E/V2401,S239D/A330Y/I332E/V264T, S239D/A330Y/I332F/K326E, andS239D/A330Y/I332E/K326T, numbered according to the EU index of Kabat.

In another example, the constant region or Fc region binds to FcγRIIamore efficiently than to FcγRIIb. For example, the constant region or Fcregion comprises at least one amino acid substitution at a positionselected from the group consisting of: 234, 235, 239, 240, 264, 296,330, and I332, numbered according to the EU index of Kabat. In oneexample, the constant region or Fc region comprises at least one aminoacid substitution selected from the group consisting of: L234Y, L234I,L2351, S239D, S239E, S239N, S239Q, V240A, V240M, V264I, V264Y, Y296Q,A330L, A330Y, A3301, 1332D, and I332E, numbered according to the EUindex of Kabat. For example, the constant region or Fc region comprisesamino acid substitutions selected from the group consisting of: I332E,V264I/I332E, S239E/I332E, S239Q/I332E, Y296Q, A330L, A330Y, I332D,S239D, S239D/I332E, A330Y/I332E, V2641/A330Y/I332E, A330I/I332E,V264I/A330L/A332E, L234Y, L234I, L235I, V240A, V240M, V264Y, A3301,S239D/A330L/I332E, S239D/S298A/I332E, S239N/S298A/I332E,S239D/V264I/I332E, S239D/V2641/S298A/I332E, and S239D/V264I/A330L/I332E,numbered according to the EU index of Kabat.

In a further example, the constant region or Fc region induces ADCC at alevel greater than that mediated by a wild-type constant region or Fecregion. For example, the constant region or Fc region induces ADCC at alevel that is more than 5-fold or between 5-fold and 1000-fold greaterthan that induced by a wild-type constant region or Fc region. In oneexample, the constant region or Fc region comprises at least one aminoacid substitution at a position selected from the group consisting of:230, 233, 234, 235, 239, 240, 243, 264, 266, 272, 274, 275, 276, 278,302, 318, 324, 325, 326, 328, 330, 332, and 335, numbered according tothe EU index of Kabat. In one example, the constant region or Fc regioncomprises at least one amino acid substitutions selected from the groupconsisting of: P230A, E233D, L234E, L234Y, L234I, L235D, L235S, L235Y,L2351, S239D, S239E, S239N, S239Q, S239T, V240I, V240M, F243L, V264I,V264T, V264Y, V266I, E272Y, K274T, K274E, K274R, K274L, K274Y, F275W,N276L, Y278T, V3021, E318R, S324D, S3241, S324V, N325T, K326I, K326T,L328M, L328I, L328Q, L328D, L328V, L328T, A330Y, A330L, A330I, I332D,I332E, I332N, I332Q, T335D, T335R, and T335Y, numbered according to theEU index of Kabat. In one example, the constant region or Fc regioncomprises amino acid substitutions selected from the group consistingof: V2641, F243ULV2641, L328M, I332E, 1328M/I332E, V264I/I332E,S298A/I332E, S239E/I332E, S239Q/I332E, S239E, A330Y, I332D, L328I/I332E,L328Q/I332E, V264T, V2401, V2661, S239D, S239D/I332D, S239D/I332E,S239D/I332N, S239D/I332Q, S239FEI332D, S239E/I332N, S239E/I332Q,S239N/I332D, S239N/I332E, S239Q/I332D, A330Y/I332F, V2641/A330Y/I332E,A330L/I332E, V264I/A330L/I332E, L234E, L234Y, L234I, L235D, L23SS,L235Y, L235I, S239T, V240M, V264Y, A3301, N325T, 1328D/I332E,I328V/I332E, L328T/I332E, L328I/I332E, S239E/V264I/I332E,S239Q/V264I/I332E, S239E/V2641/A330Y/I332E, S239D/A330Y/I332E,S239N/A330Y/I332E, S239D/A330Y/I332E, S239N/A330Y/I332E,V264I/S298A/I332E, S239D/S298A/I332E, S239N/S298A/I332E,S239D/V264I/I332E, S239D/V264I/S298A/I332E, S239D/V264I/A330Y/I332F,S239D/I332E/A330I, P230A, P230A/E233D/I332E, E272Y, K274T, K274E, K274R,K274I, K274Y, F275W, N276L, Y278T, V302I, E318R, S324D, S324T, S324V,K326I, K326T, T335D, T335R, T335Y, V240I/V266I, S239D/A330Y/I332F/L234I,S239D/A330Y/I332E/L235D, S239D/A330Y/I332E/V240I,S239D/A330Y/I332E/V264T, S239D/A330Y/I332E/K326E, andS239D/A330Y/I332E/K326T, numbered according to the EU index of Kabat.

In one example, the constant region or Fc region comprises the followingamino acid substitutions S239D/I332E, numbered according to the EU indexof Kabat. This constant region or Fc region has about 14 fold increasein affinity for FcγRIIIa compared to a wild-type constant region or Fcregion and about 3.3 increased ability to induce ADCC compared to awild-type constant region or Fc region. In one example, the constantregion comprises a sequence set forth between residues 121-450(inclusive) of SEQ ID NO: 11. In one example, the Fc region comprises asequence set forth between residues 234-450 of SEQ ID NO: 11.

In one example, the constant region or Fc region comprises the followingamino acid substitutions S239D/A3301A332E, numbered according to the EUindex of Kabat. This constant region or Fc region has about 138 foldincrease in affinity for FcγRIIIa compared to a wild-type constantregion or Fc region and about 323 increased ability to induce ADCCcompared to a wild-type constant region or Fc region. In one example,the constant region comprises a sequence set forth between residues121-450 (inclusive) of SEQ ID NO: 12. In one example, the FPc regioncomprises a sequence set forth between residues 234-450 of SEQ ID NO:12.

Additional amino acid substitutions that increase ability of a Fc regionto induce effector function are known in the art and/or described, forexample, in U.S. Pat. No. 6,737,056 or U.S. Pat. No. 7,317,091.

In one example, the glycosylation of the constant region or Fc region isaltered to increase its ability to induce enhanced effector function. Inthis regard, native antibodies produced by mammalian cells typicallycomprise a branched, biantennary oligosaccharide that is generallyattached by an N-linkage to Asn297 of the C_(H)2 domain of the constantregion or Fc region. The oligosaccharide may include variouscarbohydrates, e.g., mannose, N-acetyl glucosamine (GlcNAc), galactose,and sialic acid, as well as a fucose attached to a GlcNAc in the “stem”of the biantennary oligosaccharide structure. In some examples, constantregions or Fc regions according to the present disclosure comprise acarbohydrate structure that lacks fucose attached (directly orindirectly) to an Fc region, i.e., the Fc region is “afucosylated”. Suchvariants may have an improved ability to induce ADCC. Methods forproducing afucosylated antibodies include, expressing the immunoglobulinor antibody in a cell line incapable of expressingα-1,6-fucosyltransferase (FUTS) (e.g., as described in Yumano-Ohnuki etal., Biotechnol. Bioengineer., 87: 614-622, 2004), expressing theimmunoglobulin or antibody in cells expressing a small interfering RNAagainst FUT8 (e.g., as described in Mori et al., Biotechnol.Bioengineer., 88: 901-908, 2004), expressing the immunoglobulin orantibody in cells incapable of expressing guanosine diphosphate(GDP)-mannose 4,6-dehydratase (GMD) (e.g., as described in Kanda et al.,J. Biotechnol., 130: 300-310, 2007). The present disclosure alsocontemplates the use of immunoglobulins having a reduced level offucosylation, e.g., produced using a cell line modified to expressβ-(1,4)-N-acetylglucosaminyltransferase III (GnT-III) (e.g., asdescribed in Umäna et al., Nat. Biotechnol., 17: 176-180, 1999).

In one example, an immunoglobulin or antibody according to the presentdisclosure is afucosylated. For example, the immunoglobulin or antibodyis produced in a cell (e.g., a mammalian cell, such as a CHO cell) thatdoes not express FUT8.

Other methods include the use of cell lines which inherently produceantibodies capable of inducing enhanced Fc-mediated effector function(e.g. duck embryonic derived stem cells for the production of viralvaccines, WO2008/129058; Recombinant protein production in avian EBX®cells, WO 2008/142124).

Immunoglobulins useful in the methods of the present disclosure alsoinclude those with bisected oligosaccharides, e.g., in which abiantennary oligosaccharide attached to the constant region or Fc regionis bisected by GlcNAc. Such immunoglobulins may have reducedfucosylation and/or improved ADCC function. Examples of suchimmunoglobulins are described, e.g., in U.S. Pat. No. 6,602,684 andUS20050123546.

Immunoglobulins with at least one galactose residue in theoligosaccharide attached to the constant region or Fc region are alsocontemplated. Such immunoglobulins may have improved CDC function. Suchimmunoglobulins are described, e.g., in WO1997/30087 and WO1999/22764.

Non-limiting examples of immunoglobulins that induce enhanced levels ofADCC activity include:

(i) an antibody comprising a heavy chain comprising a sequence set forthin SEQ ID NO: 11 and a light chain comprising a sequence set forth inSEQ ID NO: 13;(ii) an antibody comprising a heavy chain comprising a sequence setforth in SEQ ID NO: 12 and a light chain comprising a sequence set forthin SEQ ID NO: 13; and(iii) an antibody comprising a heavy chain comprising a sequence setforth in SEQ ID NO: 10 and a light chain comprising a sequence set forthin SEQ ID NO: 13, wherein the heavy chain constant region isafucosylated.

An advantageous antibody of the disclosure that induces enhanced levelsof ADCC activity comprises a heavy chain comprising a sequence set forthin SEQ ID NO: 11 and a light chain comprising a sequence set forth inSEQ ID NO: 13. As discussed herein, after administering this antibody toa mammal (e.g., at least 7 or 8 or 11 or 17 or 22 or 29 days afteradministration) the number of NK cells in a mammal is increased comparedto one or more of:

(i) the number of NK cells in the mammal prior art administration of theantibody;(ii) the number of NK cells in a mammal administered an antibodycomprising a heavy chain comprising a sequence set forth in SEQ ID NO:10 and a light chain comprising a sequence set forth in SEQ ID NO: 13,wherein the heavy chain constant region is afucosylated (e.g., asassessed on the same day after administration); and(iii) the number of NK cells in a mammal administered an antibody thatbinds specifically to II3Rα chain and has a human IgG1 constant region(e.g., as assessed on the same day after administration).

Methods for determining the ability of an immunoglobulin or antibody toinduce effector function and known in the art and/or described in moredetail herein.

Additional Modifications

The present disclosure also contemplates additional modifications to animmunoglobulin.

For example, the immunoglobulin or antibody comprises one or more aminoacid substitutions that increase the half-life of the immunoglobulin.For example, the immunoglobulin or antibody comprises a constant regionor Fc region comprising one or more amino acid substitutions thatincrease the affinity of the constant region or Fc region for theneonatal Pc region (FcRn). For example, the constant region or Fc regionhas increased affinity for FcRn at lower pH, e.g., about pH 6.0, tofacilitate Fc/FcRn binding in an endosome. In one example, the constantregion or Fc region has increased affinity for FcRn at about pH 6compared to its affinity at about pH 7.4, which facilitates there-release of constant region or Fc into blood following cellularrecycling. These amino acid substitutions are useful for extending thehalf life of an immunoglobulin, by reducing clearance from the blood.

Exemplary amino acid substitutions include T250Q and/or M428L accordingto the EU numbering system of Kabat. Additional or alternative aminoacid substitutions are described, for example, in US20070135620.

Nucleic Acids

Another example of the disclosure provides an isolated nucleic acid thatencodes an immunoglobulin or antibody of the disclosure, inclusive offragments, variants and derivatives of the immunoglobulin or antibody.

Certain examples of nucleic acids comprise a nucleotide sequence setforth in one or more of SEQ ID NOS:14-19, which respectively encodeCDRs1-6 of an immunoglobulin or antibody of the disclosure.

Other examples of nucleic acids comprise a nucleotide sequence set forthin one or more of SEQ ID NOS: 20-23.

The disclosure also contemplates nucleic acid homologs that encode avariant of an immunoglobulin or antibody of the disclosure, ashereinbefore described.

Exemplary, nucleic acid homologs share at least 80% or 85%, such as atleast 90% or 95% or 99% nucleotide sequence identity with an isolatednucleic acid that encodes any one of SEQ ID NOS:2-13. Suitably, thenucleic acid homolog does not encode a protein comprising a murinevariable region capable of binding specifically to IL-3Rα.

Nucleic acid homologs may hybridize to isolated nucleic acids of thedisclosure under high stringency conditions.

Protein Production Recombinant Expression

In one example, an immunoglobulin or antibody described herein accordingto any example is recombinant.

By way of example only, a recombinant immunoglobulin or antibody of thedisclosure may be produced by a method including the steps of:

-   -   (i) preparing an expression construct which comprises an        isolated nucleic acid of disclosure, operably linked to one or        more regulatory nucleotide sequences (e.g., a promoter);    -   (ii) transfecting or transforming a suitable host cell with the        expression construct;    -   (iii) expressing a recombinant immunoglobulin or antibody in the        host cell; and    -   (iv) isolating the recombinant immunoglobulin or antibody from        the host cell.

In the case of a recombinant immunoglobulin, nucleic acid encoding samecan be cloned into expression vectors, which are then transfected intohost cells, such as E. coli cells, yeast cells, insect cells, ormammalian cells, such as simian COS cells, Chinese Hamster Ovary (CHO)cells, human embryonic kidney (HEK) cells, or myeloma cells that do nototherwise produce immunoglobulin or antibody protein.

Exemplary cells used for expressing an immunoglobulin or antibody areCHO cells, myeloma cells or HEK cells. The cell may further comprise oneor more genetic mutations and/or deletions that facilitate expression ofa modified immunoglobulin or antibody. One non-limiting example is adeletion of a gene encoding an enzyme required for fucosylation of anexpressed immunoglobulin or antibody. For example, the deleted geneencodes FUT8. A commercially available source of FUT8-deleted CHO cellsis Biowa (Potelligent™ cells). For example, the cells used forexpression of an afucosylated immunoglobulin or antibody areFUT8-deleted CHO cells, such as, Biowa's Potelligent™ cells.

Molecular cloning techniques to achieve these ends are known in the artand described, for example in Ausubel et al., (editors), CurrentProtocols in Molecular Biology, Greene Pub. Associates andWiley-Interscience (1988, including all updates until present) orSambrook et al., Molecular Cloning: A Laboratory Manual, Cold SpringHarbor Laboratory Press (1989). A wide variety of cloning and in vitroamplification methods are suitable for the construction of recombinantnucleic acids. Methods of producing recombinant antibodies are alsoknown in the art. See U.S. Pat. No. 4,816,567 or U.S. Pat. No.5,530,101.

Following isolation, the nucleic acid is inserted operably linked to apromoter in an genetic construct or expression vector for furthercloning (amplification of the DNA) or for expression in a cell-freesystem or in cells. Thus, another example of the disclosure provides agenetic construct that comprises an isolated nucleic acid of thedisclosure and one or more additional nucleotide sequences. Suitably,the genetic construct is in the form of, or comprises genetic componentsof, a plasmid, bacteriophage, a cosmid, a yeast or bacterial artificialchromosome as are well understood in the art. Genetic constructs may besuitable for maintenance and propagation of the isolated nucleic acid inbacteria or other host cells, for manipulation by recombinant DNAtechnology and/or for expression of the nucleic acid or an encodedimmunoglobulin or antibody of the disclosure. For the purposes of hostcell expression, the genetic construct is an expression construct.Suitably, the expression construct comprises the nucleic acid of thedisclosure operably linked to one or more additional sequences in anexpression vector, such as a promoter or a regulatory sequence.

Typically, a regulatory nucleotide sequence may include, but are notlimited to, promoter sequences, leader or signal sequences, ribosomalbinding sites, transcriptional start and termination sequences,translational start and termination sequences, and enhancer or activatorsequences.

As used herein, the term “promoter” is to be taken in its broadestcontext and includes the transcriptional regulatory sequences of agenomic gene, including the TATA box or initiator element, which isrequired for accurate transcription initiation, with or withoutadditional regulatory elements (e.g., upstream activating sequences,transcription factor binding sites, enhancers and silencers) that alterexpression of a nucleic acid, e.g., in response to a developmentaland/or external stimulus, or in a tissue specific manner. In the presentcontext, the term “promoter” is also used to describe a recombinant,synthetic or fusion nucleic acid, or derivative which confers, activatesor enhances the expression of a nucleic acid to which it is operablylinked. Exemplary promoters can contain additional copies of one or morespecific regulatory elements to further enhance expression and/or alterthe spatial expression and/or temporal expression of said nucleic acid.

As used herein, the term “operably linked to” means positioning apromoter relative to a nucleic acid such that expression of the nucleicacid is controlled by the promoter.

Many vectors for expression in cells are available. The vectorcomponents generally include, but are not limited to, one or more of thefollowing: a signal sequence, a sequence encoding an immunoglobulin orantibody (e.g., derived from the information provided herein), anenhancer element, a promoter, and a transcription termination sequence.The skilled artisan will be aware of suitable sequences for expressionof an immunoglobulin. Exemplary signal sequences include prokaryoticsecretion signals (e.g., pelB, alkaline phosphatase, penicillinase, lpp,or heat-stable enterotoxin IT), yeast secretion signals (e.g., invertaseleader, a factor leader, or acid phosphatase leader) or mammaliansecretion signals (e.g., herpes simplex gD signal).

Exemplary promoters active in mammalian cells include cytomegalovirusimmediate early promoter (CMV-IE), human elongation factor 1-α promoter(EF1), small nuclear RNA promoters (U1a and U1b), α-myosin heavy chainpromoter, Simian virus 40 promoter (SV40), Rous sarcoma virus promoter(RSV), Adenovirus major late promoter, β-actin promoter; hybridregulatory element comprising a CMV enhancer/β-actin promoter or animmunoglobulin or antibody promoter or active fragment thereof. Examplesof useful mammalian host cell lines are monkey kidney CV1 linetransformed by SV40 (COS-7, ATCC CRL 1651); human embryonic kidney line(293 or 293 cells subeloned for growth in suspension culture; babyhamster kidney cells (BHK, ATCC CCL 10); or Chinese hamster ovary cells(CHO).

Typical promoters suitable for expression in yeast cells such as forexample a yeast cell selected from the group comprising Pichla pastoris.Saccharomyces cerevisiae and S. pombe, include, but are not limited to,the ADH1 promoter, the GAL1 promoter, the GAL4 promoter, the CUP1promoter, the PHO5 promoter, the nmt promoter, the RPR1 promoter, or theTEF1 promoter.

Means for introducing the isolated nucleic acid or expression constructcomprising same into a cell for expression are known to those skilled inthe art. The technique used for a given cell depends on the knownsuccessful techniques. Means for introducing recombinant DNA into cellsinclude microinjection, transfection mediated by DEAE-dextran,transfection mediated by liposomes such as by using lipofectamine(Gibco, MD, USA) and/or cellfectin (Gibco, MD, USA), PEG-mediated DNAuptake, electroporation and microparticle bombardment such as by usingDNA-coated tungsten or gold particles (Agracetus Inc., WI, USA) amongstothers.

The host cells used to produce the immunoglobulin or antibody may becultured in a variety of media, depending on the cell type used.Commercially available media such as Ham's F10 (Sigma), MinimalEssential Medium ((MEM), (Sigma), RPMI-1640 (Sigma), and Dulbooco'sModified Eagle's Medium ((DMEM), Sigma) are suitable for culturingmammalian cells. Media for culturing other cell types discussed hereinare known in the art.

Isolation of Proteins

Methods for purifying an immunoglobulin or antibody are known in the artand/or described herein.

Where an immunoglobulin or antibody is secreted into the medium,supernatants from such expression systems can be first concentratedusing a commercially available protein concentration filter, forexample, an Amicon or Millipore Pellicon ultrafiltration unit. Aprotease inhibitor such as PMSF may be included in any of the foregoingsteps to inhibit proteolysis and antibiotics may be included to preventthe growth of adventitious contaminants.

The immunoglobulin or antibody prepared from the cells can be purifiedusing, for example, ion exchange, hydroxyapatite chromatography,hydrophobic interaction chromatography, gel electrophoresis, dialysis,affinity chromatography (e.g., protein A affinity chromatography orprotein G chromatography), or any combination of the foregoing. Thesemethods are known in the art and described, for example in WO99/57134 orEd Harlow and David Lane (editors) Antibodies: A Laboratory Manual, ColdSpring Harbour Laboratory, (1988).

The skilled artisan will also be aware that an immunoglobulin orantibody can be modified to include a tag to facilitate purification ordetection, e.g., a poly-histidine tag, e.g., a hexa-histidine tag, or ainfluenza virus hemagglutinin (HA) tag, or a Simian Virus 5 (V5) tag, ora FLAG tag, or a glutathione S-transferase (GST) tag. The resultingimmunoglobulin or antibody is then purified using methods known in theart, such as, affinity purification. For example, an immunoglobulin orantibody comprising a hexa-his tag is purified by contacting a samplecomprising the immunoglobulin or antibody with nickel-nitrilotriaceticacid (Ni-NTA) that specifically binds a hexa-his tag immobilized on asolid or semi-solid support, washing the sample to remove unboundimmunoglobulin, and subsequently eluting the bound immunoglobulin.Alternatively, or in addition a ligand or antibody that binds to a tagis used in an affinity purification method.

In one example, the immunoglobulin or antibody also has a proteasecleavage site, such as for Factor X_(a) or Thrombin, which allow therelevant protease to partially digest the immunoglobulin or antibody andthereby liberate the immunoglobulin or antibody from the tag. Theliberated antibody or immunoglobulin can then be isolated from thefusion partner by subsequent chromatographic separation.

Assaying Activity of an Immunoglobulin

Immunoglobulins or antibodies of the disclosure are readily screened forbiological activity, e.g., as described below.

Binding Assays

One form of such an assay is an antigen binding assay, e.g., asdescribed in Scopes (In: Protein purification: principles and practice,Third Edition, Springer Verlag, 1994). Such a method generally involveslabeling the immunoglobulin or antibody and contacting it withimmobilized antigen. Following washing to remove non-specific boundprotein, the amount of label and, as a consequence, bound protein isdetected. Of course, the immunoglobulin or antibody can be immobilizedand the antigen labeled. Panning-type assays, e.g., as described orexemplified herein can also be used.

Determining Neutralization

In some examples of the present disclosure, an immunoglobulin orantibody is capable of neutralizing IL-3 signaling.

Various assays are known in the art for assessing the ability of animmunoglobulin to neutralize signaling of a ligand through a receptor.

In one example, the immunoglobulin or antibody reduces or prevents IL-3binding to the 3Rα chain and/or a heterodimer of IL-3Rα chain and IL-3Rβchain.

These assays can be performed as a competitive binding assay usinglabeled IL-3 and/or labeled immunoglobulin. For example, labeled IL-3Rαor an extracellular region thereof fused to an Fc region of an antibodyor a cell expressing IL-3R immobilized and labeled IL-3 is thencontacted to the immobilized receptor or cell in the presence or absenceof a test immunoglobulin or antibody and the amount of bound labeldetected. A reduction in the amount of bound label in the presence ofthe antibody or immunoglobulin compared to in the absence of the proteinindicates that the immunoglobulin or antibody reduces or preventsbinding of IL-3 to IL-3R. By testing multiple concentrations of theimmunoglobulin or antibody an IC₅₀ is determined, i.e., a concentrationof the protein that reduces the amount of IL-3 that binds to IL-3R, oran EC₅₀ can be determined, i.e., a concentration of the protein thatachieves 50% of the maximum inhibition of binding of IL-3 to IL-3Rachieved by the immunoglobulin or antibody

In another example, the immunoglobulin or antibody reduces or preventsIL-3-mediated histamine release from basophils. For example, low densityleukocytes comprising basophils are incubated with IgE, IL-3 and variousconcentrations of the immunoglobulin or antibody. Control cells do notcomprise immunoglobulin (positive control) or IL-3 (negative control).The level of released histamine is then assessed using a standardtechnique, e.g., RIA. An immunoglobulin or antibody that reduces thelevel of histamine release to a level less than the positive control isconsidered to neutralize IL-3 signaling. In one example, the level ofreduction is correlated with immunoglobulin or antibody concentration.An exemplary method for assessing IL-3-mediated histamine release isdescribed, for example, in Lopez et al., J. Cell. Physiol., 145: 69,1990.

In a further example, the immunoglobulin or antibody reduces or preventsIL-3-mediated proliferation of leukemic cell line TF-1. For example,TF-1 cells are cultured without IL-3 or GM-CSF for a time sufficient forthem to stop proliferating (e.g., 24-48 hours). Cells are then culturedin the presence of IL-3 and various concentrations of the immunoglobulinor antibody. Control cells are not contacted with the immunoglobulin orantibody (positive control) or IL-3 (negative control). Cellproliferation is then assessed using a standard technique, e.g.,³H-thymidine incorporation. An immunoglobulin or antibody that reducesor prevents cell proliferation in the presence of IL-3 to a level lessthan the positive control is considered to neutralize IL-3 signaling.

Another assay for assessing IL-3 signaling neutralization comprisesdetermining whether or not the immunoglobulin or antibody reduces orprevents IL-3-mediated effects on endothelial cells. For example, humanumbilical vein endothelial cells (HUVECs) are cultured in the presenceof IL-3 (optionally, with IPN-γ) and various concentrations of theimmunoglobulin or antibody. The amount of secreted IL-6 is thenassessed, e.g., using an enzyme linked immunosorbent assay (ELISA).Control cultures do not comprise immunoglobulin or antibody (positivecontrol) or IL-3 (negative control). An immunoglobulin or antibody thatreduces or prevents IL-6 production in the presence of IL-3 to a levelless than the positive control is considered to neutralize IL-3signaling.

Other methods for assessing neutralization of IL-3 signaling arecontemplated by the present disclosure.

Determining Effector Function

Methods for assessing ADCC activity are known in the art.

In one example, the level of ADCC activity is assessed using a ⁵¹Crrelease assay, a europium release assay or a ³⁵S release assay. In eachof these assays, cells expressing IL-3Rα are cultured with one or moreof the recited compounds for a time and under conditions sufficient forthe compound to be taken up by the cell. In the case of a ³⁵S releaseassay, cells expressing IL-3Rα can be cultured with ³⁵S-labeledmethionine and/or cysteine for a time sufficient for the labeled aminoacids to be incorporated into newly synthesized proteins. Cells are thencultured in the presence or absence of the immunoglobulin or antibodyand in the presence of immune effector cells, e.g., peripheral bloodmononuclear cells (PBMC) and/or NK cells. The amount of ⁵¹Cr, europiumand/or ³⁵S in cell culture medium is then detected, and an increase inthe presence of the immunoglobulin or antibody compared to in theabsence of immunoglobulin indicates that the immunoglobulin has effectorfunction. Exemplary publications disclosing assays for assessing thelevel of ADCC induced by an immunoglobulin include Hellstrom, et al.Proc. Natl. Acad. Sci. USA 83:7059-7063, 1986 and Bruggemann, et al., J.Exp. Med. 166:1351-1361, 1987.

Other assays for assessing the level of ADCC induced by animmunoglobulin or antibody include ACTI™ nonradioactive cytotoxicityassay for flow cytometry (CellTechnology, Inc. CA, USA) or CytoTox 96®non-radioactive cytotoxicity assay (Promega, WI, USA).

Alternatively, or additionally, effector function of an immunoglobulinor antibody is assessed by determining its affinity for one or moreFcγRs, e.g., as described in U.S. Pat. No. 7,317,091.

Clq binding assays may also be carried out to confirm that theimmunoglobulin or antibody is able to bind Clq and may induce CDC. Toassess complement activation, a CDC assay may be performed (see, forexample, Gazzano-Santoro et al. J. Immunol. Methods 202: 163, 1996.

Determining NK Cell Numbers

As discussed herein, immunoglobulins and/or antibodies of the disclosurecan affect the number of NK cells in a mammal. Methods for assessing thenumber of NK cells in a mammal will be apparent to the skilled artisan.

In one example, following administration of an immunoglobulin orantibody of the disclosure to a mammal (e.g., a non-human mammal, suchas a non-human primate, e.g., a cynomolgus monkey) a sample of blood (orserum) is obtained and the number of NK cells assessed usingfluorescence activated cell sorting (FACS). NK cells can be detectedbased on expression of CD16 and/or CD56 and/or lack of expression (orlow levels of expression) of CD20 and/or CD3.

The percentage change in the number of NK cells can be determined bycomparing to the number of NK cells in a sample obtained earlier (e.g.,prior to administration of the antibody or immunoglobulin.

Determining Affinity

Optionally, the dissociation constant (Kd) or association constant (Ka)or equilibrium constant (K_(D)) of a protein for IL-3Rα or an epitopethereof is determined. These constants for an immunoglobulin or antibodyis, in one example, measured by a radiolabeled or fluorescently-labeledIL-3Rα-binding assay. This assay equilibrates the protein with a minimalconcentration of labeled IL-3Rα (or a soluble form thereof, e.g.,comprising an extracellular region of IL-3Rα fused to an Fc region) inthe presence of a titration series of unlabeled IL-3Rα. Followingwashing to remove unbound IL-3Rα, the amount of label is determined.

Affinity measurements can be determined by standard methodology forantibody reactions, for example, immunoassays, surface plasmon resonance(SPR) (Rich and Myszka Curr. Opin. Biotechnol 11: δ 54, 2000;Englebienne Analyst. 123: 1599, 1998), isothermal titration calorimetry(ITC) or other kinetic interaction assays known in the art.

In one example, the constants are measured by using surface plasmonresonance assays, e.g., using BIAcore surface plasmon resonance(BIAcore, Inc., Piscataway, N.J.) with immobilized IL-3Rα or a regionthereof. Exemplary SPR methods are described in U.S. Pat. No. 7,229,619.

Assessing Therapeutic Efficacy In Vitro Assays

Various in vitro assays are available to assess the ability of animmunoglobulin or antibody to treat a disease or condition describedherein.

For example, an immunoglobulin or antibody is assessed for its abilityto kill a cell, e.g., a cancer cell, such as leukemic cell, using amethod described herein.

In another example, immune cells, e.g., pDCs and/or basophils or cellpopulations comprising same (e.g., PBMC) are cultured in the presence orabsence of an immunoglobulin or antibody and an inducer of those cellsthat occurs in a disease or condition (e.g., CpG oligonucleotides and/orimmune complexes). The efficacy of the immunoglobulin or antibody intreating the disease or condition is then assessed, e.g., by determiningthe level of IFNα secreted into cell culture medium using an ELISA.Alternatively or in addition the level of histamine secretion or IL-4,L-6 and/or IL-13 secretion is assessed. A reduction in the level of anyof these cytokines compared to in the absence of immunoglobulin orantibody (or in the presence of an isotype control immunoglobulin orantibody) indicates that the immunoglobulin or antibody is suitable fortreating the disease or condition. Alternatively, or in addition, thelevel of cell death is assessed. An increase in cell death is indicativeof an immunoglobulin or antibody suitable for treating the disease orcondition.

In Vivo Assays

In one example, the efficacy of an immunoglobulin to treat a disease orcondition is assessed using an in viva assay.

In one example, a xenotransplantation model of a cancer is used toassess therapeutic efficacy. For example, NOD/SCID mice are irradiatedand optionally treated with anti-CD122 antibody to deplete NK cells.Human leukemic cells (e.g., acute myeloid leukemia cells) and mouse orhuman bone marrow stem cells are administered to the mice. Followingcell engraftment, a test immunoglobulin or antibody is administered tothe mice and the level of leukemic cells in circulation and/or bonemarrow and/or lymph nodes is assessed. A reduction in the number ofleukemic cells in circulation and/or bone marrow and/or lymph nodes inthe presence of the antibody or immunoglobulin compared to in theabsence of the antibody or immunoglobulin indicates therapeuticefficacy.

In another example, the immunoglobulin or antibody is administered to anon-human animal (e.g., a non-human primate) and the number/level ofimmune cells, e.g., pDCs and/or basophils, in circulation is assessed.An immunoglobulin or antibody that reduces the number/level of immunecells, e.g., pDCs and/or basophils compared to prior to administrationand/or in a control mammal to which the immunoglobulin or antibody hasnot been administered is considered suitable for treating the disease orcondition.

In another example, the level of a cytokine, such as IFNα is detected inthe circulation of a mammal, e.g., using an ELISA. An immunoglobulin orantibody that reduces the level of the cytokine compared to the levelprior to administration and/or in a control mammal to which theimmunoglobulin or antibody has not been administered is consideredsuitable for treating the disease or condition. Since cytokines such asIFNα are considered to play a role in some diseases/conditions, e.g.,lupus, an immunoglobulin or antibody that reduces IFNα production isconsidered to be suitable for treating such conditions.

Compositions

Suitably, in compositions or methods for administration of theanti-IL-3Rα immunoglobulin or antibody to a mammal, the immunoglobulinor antibody is combined with a pharmaceutically acceptable carrier,diluent and/or excipient, as is understood in the art. Accordingly, oneexample of the present disclosure provides a pharmaceutical compositioncomprising the immunoglobulin or antibody of the disclosure combinedwith a pharmaceutically acceptable carrier, diluent and/or excipient. Inanother example, the disclosure provides a kit comprising apharmaceutically acceptable carrier, diluent and/or excipient suitablefor combining or mixing with the immunoglobulin or antibody prior toadministration to the mammal. In this example, the kit may furthercomprise instructions for use.

In general terms, by “carrier, diluent or excipient” is meant a solid orliquid filler, binder, diluent, encapsulating substance, emulsifier,wetting agent, solvent, suspending agent, coating or lubricant that maybe safely administered to any mammal, e.g., a human. Depending upon theparticular route of administration, a variety of acceptable carriers,diluents or excipients, known in the art may be used, as for exampledescribed in Remington's Pharmaceutical Sciences (Mack Publishing Co.NJ. USA, 1991).

By way of example only, the carriers, diluents or excipients may beselected from a group including sugars (e.g. sucrose, maltose,trehalose, glucose), starches, cellulose and its derivatives, malt,gelatine, talc, calcium sulphate, oils inclusive of vegetable oils,synthetic oils and synthetic mono- or di-glycerides, lower alcohols,polyols, alginic acid, phosphate buffered solutions, lubricants such assodium or magnesium stearate, isotonic saline and pyrogen-free water.For example, the carrier, diluent or excipient is compatible with, orsuitable for, parenteral administration. Parenteral administrationincludes any route of administration that is not through the alimentarycanal. Non-limiting examples of parenteral administration includeinjection, infusion and the like. By way of example, administration byinjection includes intravenous, intra-arterial, intramuscular andsubcutaneous injection. Also contemplated is delivery by a depot orslow-release formulation which may be delivered intradermally,intramuscularly and subcutaneously, for example.

Combination Therapies

In one example, the immunoglobulin or antibody of the disclosure isadministered in combination with another compound or therapeutictreatment useful for treating a disease or condition.

In one example, the immunoglobulin or antibody is administered prior to,e.g., one month or one fortnight or one week prior to radiation therapy,e.g., for the treatment of cancer, such as a hematologic cancer, such asleukemia.

In one example, the other compound is a chemotherapy compound, such ascaboplatin, cisplatin, cyclophosphamide, docetaxal, doxorubicin,erlotinib, etoposide, fluorouracil, irinotecan, methotrexate,paclitaxel, topotecan, vincristine or vinblastine. In one example, thechemotherapy compound is selected from the group consisting ofmethotrexate, 1-asparaginase, vincristine, doxorubicin, danorubicin,cytarabine, idarubicin, mitoxantrone, cyclophosphamide, fludarabine,chlorambucil and combinations thereof.

In one example, the other compound is a chemotherapy compound used inthe treatment of acute leukemia, such as, a compound selected from thegroup consisting of methotrexate, 1-asparaginase, vincristine,doxorubicin, danorubicin, cytarabine, idarubicin, mitoxantrone andcombinations thereof.

In one example, the other compound is a chemotherapy compound used inthe treatment of acute lymphoblastic leukemia, such as, a compoundselected from the group consisting of methotrexate, 1-asparaginase,vincristine, doxorubicin, danorubicin and combinations thereof.

In a further example, the other compound is a chemotherapy compound suchas azacytidine.

In one example, the other compound is a biologic useful for treating acancer, e.g., rituximab, trastuumab, bevacizumab, alemtuzumab,panitumumab, or cetuximab

In one example, the other compound is an anti-inflammatory compound.Alternatively, or additionally, the other compound is animmunosuppressant. Alternatively, or additionally, the other compound isa corticosteroid, such as prednisone and/or prednisolone. Alternatively,or additionally, the other compound is an antimalarial compound, such ashydroxychloroquine or chloroqulnine. Alternatively, or additionally, theother compound is methotrexate. Alternatively, or additionally, theother compound is azathioprine.

Alternatively, or additionally, the other compound is cyclophosphamide.Alternatively, or additionally, the other compound is mycophenolatemofetil. Alternatively, or additionally, the other compound is ananti-CD20 antibody (e.g., rituximab or ofatumumab). Alternatively, oradditionally, the other compound is an anti-CD22 antibody (e.g.,epratuzumab). Alternatively, or additionally, the other compound is ananti-TNF antibody (e.g., infliximab or adalimumab or golimumab).Alternatively, or additionally, the other compound is a CTLA-4antagonist (e.g., abatacept, CTLA4-Ig). Alternatively, or additionally,the other compound is an anti-IL-6 antibody. Alternatively, oradditionally, the other compound is a BLys antagonist, such as ananti-BLys antibody (e.g., belimumab).

Dosages and Timing of Administration

For the prevention or treatment of a disease or condition or relapsethereof, the appropriate dosage of an active agent (i.e., animmunoglobulin or antibody of the disclosure), will depend on the typeof disease to be treated, the severity and course of the disease,whether the immunoglobulin or antibody is administered for preventive ortherapeutic purposes, previous therapy, the patient's clinical historyand response to the immunoglobulin, and the discretion of the attendingphysician. The particular dosage regimen, i.e., dose, timing, andrepetition, will depend on the particular individual and thatindividual's medical history as assessed by a physician. Typically, aclinician will administer an immunoglobulin until a dosage is reachedthat achieves the desired result.

Methods of the present disclosure are useful for treating, amelioratingor preventing the symptoms of diseases or conditions in a mammal, or forimproving the prognosis of a mammal. Methods of the present disclosureare also useful for delaying development of or preventing lupus in anindividual at risk of developing lupus or a relapse thereof.

For administration of the immunoglobulins or antibodies describedherein, normal dosage amounts may vary from about 10 ng/kg up to about100 mg/kg of an individual's body weight or more per day. Exemplarydosages and ranges thereof are described herein. For repeatedadministrations over several days or longer, depending on the severityof the disease or disorder to be treated, the treatment can be sustaineduntil a desired suppression of symptoms is achieved.

In some examples, the immunoglobulin or antibody is administered at aninitial (or loading) dose of between about 1 mg/kg to about 30 mg/kg,such as from about 1 mg/kg to about 10 mg/kg, or about 2 mg/kg or about3 mg/kg or 4 mg/kg or 5 mg/kg. The immunoglobulin or antibody can thenbe administered at a maintenance dose of between about 0.0001 mg/kg toabout 1 mg/kg, such as from about 0.0005 mg/kg to about 1 mg/kg, forexample, from about 0.001 mg/kg to about 1 mg/kg, such as about 0.01mg/kg to about 1 mg/kg, for example from about 0.01 mg/kg to about 0.1mg/kg, such as about 0.02 mg/kg or 0.03 mg/kg or 0.04 mg/kg or 0.05mg/kg. The maintenance doses may be administered every 7-30 days, suchas, every 10-15 days, for example, every 10 or 11 or 12 or 13 or 14 or15 days.

In some examples, the immunoglobulin or antibody is administered at adose of between about 0.0001 mg/kg to about 50 mg/kg, such as betweenabout 0.0005 mg/kg to about 50 mg/kg, for example, between about 0.001mg/kg to about 40 mg/kg, for example, between about 0.005 mg/kg to about30 mg/kg, such as between about 0.01 mg/kg to about 20 mg/kg. Forexample, the immunoglobulin is administered at a dose of between about0.01 mg/kg to about 10 mg/kg, such as from about 0.01 mg/kg to about 1mg/kg, such as about 0.02 mg/kg or 0.03 mg/kg or 0.04 mg/kg or 0.05mg/kg or 0.06 mg/kg or 0.07 mg/kg or 0.08 mg/kg or 0.09 mg/kg or 0.1mg/kg or 0.2 mg/kg or 0.3 mg/kg or 0.4 mg/kg or 0.5 mg/kg or 0.6 mg/kgor 0.7 mg/kg or 0.8 mg/kg or 0.9 mg/kg (e.g., without a higher loadingdose). In some examples, numerous doses are administered, e.g., every7-30 days, such as, every 10-22 days, for example, every 10-15 days, forexample, every 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19or 20 or 21 or 22 days. For example, the immunoglobulin or antibody isadministered every 7 days or every 14 days or every 21 days.

In some examples, the immunoglobulin or antibody is administered at adose of between about 1 mg/kg to about 30 mg/kg, such as from about 1mg/kg to about 10 mg/kg, or about 2 mg/kg or about 3 mg/kg or 4 mg/kg or5 mg/kg, or such as from about 10 mg/kg to 30 mg/kg, such as about 10mg/kg or 15 mg/kg or 20 mg/kg or 25 mg/kg (e.g., without a lowermaintenance dose). In some examples, numerous doses are administered,e.g., every 10-70 days, such as every 14-70 days, such as, every 14-60days, for example, every 14-50 days, such as every 14-40 days, or every14-30 days. For example the doses are administered every 14 or 21 or 25or 28 or 35 or 40 or 42 or 49 or 50 or 55 or 57 or 63 or 70 days. Forexample, the immunoglobulin or antibody is administered every 21 days orevery 28 days or every 35 days or every 42 days or every 49 days orevery 56 days.

In some examples, the immunoglobulin or antibody causes or is associatedwith a reduction of NK cells in a mammal following administration, e.g.,within about 6 hours of administration. In some examples, a further doseof the immunoglobulin or antibody is administered when the number of NKcells in a mammal returns to within 20% or 10% or 5% or 1% of the numberof NK cells in the mammal prior to administration. In some examples, afurther dose of the immunoglobulin or antibody is administered when thenumber of NK cells in a mammal exceeds the number of NK cells in themammal prior to administration by at least about 5% or 10% or 20% or 30%or 40% or 50% or 60% or 70% or 80%. The number of NK cells can beassessed in a mammal to determine when to administer the further dose ofthe immunoglobulin or antibody. Alternatively, the time to administer afurther dose of the immunoglobulin or antibody is determined by previousanalysis of a population or a model organism (e.g., a non-human primate,such as a cynomolgus monkey). For example, the further dose of theimmunoglobulin is administered about 7 days or 8 days or 14 days or 17days or 21 days or 22 days or 28 days or 29 days following a previousdose.

In some examples, at the time of commencing therapy, the mammal isadministered the immunoglobulin or antibody on no more than 7consecutive days or 6 consecutive days or 5 consecutive days or 4consecutive days.

In the case of a mammal that is not adequately responding to treatment,multiple doses in a week may be administered. Alternatively, or inaddition, increasing doses may be administered.

In another example, for mammals experiencing an adverse reaction, theinitial (or loading) dose may be split over numerous days in one week orover numerous consecutive days.

Dosages for a particular immunoglobulin or antibody may be determinedempirically in mammals that have been given one or more administrationsof the immunoglobulin. To assess efficacy of an immunoglobulin, aclinical symptom of a disease or condition can be monitored.

Administration of an immunoglobulin according to the methods of thepresent disclosure can be continuous or intermittent, depending, forexample, on the recipient's physiological condition, whether the purposeof the administration is therapeutic or prophylactic, and other factorsknown to skilled practitioners. The administration of an immunoglobulinor antibody may be essentially continuous over a preselected period oftime or may be in a series of spaced doses, e.g., either during or afterdevelopment of a condition.

The present disclosure includes the following non-limiting examples.

NON-LIMITING EXAMPLES Example 1 Humanized Antibodies

A humanized antibody that binds specifically to human IL-3Rα chain thatacts as an antagonist of IL-3 activity was produced. The humanizedantibody was produced by grafting CDR sequences of an antagonisticmurine antibody (7G3) onto human variable framework germline sequencesselected on the basis of the canonical structure of the donor andacceptor CDRs in accordance with the procedure of Tan et al., (JImmunol. 169, 1119-1125, 2002); sometimes referred to as“superhumanization”. This work was conducted using the antibody in ascFv format. This approach then compares the CDR residues of the donorantibody with those of the variable framework germline acceptorsequences, and selects as the acceptor sequence the one with highestcorrelation of CDR residues. However, in the present case a heavy chainacceptor sequence with a lower level of CDR correlation was selected.The resulting humanized antibody contained entirely human variableframework sequence as a result of the humanization process, however theaffinity for IL-3Rα was decreased compared with the parental murineantibody.

Affinity optimization was employed using a ribosome display-basedmutagenesis process (Kopsidas et al., BMC Biotechnol. 7, 18, 2007)conducted using the antibody in a scFv format in an effort to increasethe binding affinity of the humanized antibody. An affinity optimizedscFv was produced that when converted to an IgG₁ format exhibitedslightly improved IL-3Rα binding affinity to that of the parent murinemonoclonal antibody. Unpredictably, the affinity optimization processresulted in mutations in the framework of the V_(H) and V_(L) as well asin CDR1 of the light chain. So the set of CDR sequences of the humanizedaffinity optimized antibody differs from those of the parent murinemonoclonal antibody. There affinity optimized antibody is referred toherein as CSL362.

Fc engineered derivatives of the humanized affinity optimized antibodycomprising the light and heavy chain variable regions of the antibodyand a hybrid IgG₁/IgG2 constant domain with the three amino acidsubstitutions S239D/A330L/A332E (referred to herein as CSL362X2) or withthe two amino acid substitutions S239D/I332E (referred to herein asCSL362X1) were produced by expression of an appropriate vector in CHO-Scells; the positions of the identified mutations are based on EUnumbering system.

An afucosylated version of humanized affinity optimized antibody with ahuman IgG₁ constant domain was generated by expression of an appropriatevector in FUT8-knock-out CHO cells from Biowa (Potelligent® Cells)(referred to herein as CSL362B).

Example 2 Binding Affinity Determination Full-Length mAb Kinetics:

To analyze full-length antibodies, surface plasmon resonance (Biacore)assays were performed in a capture format where a chemically immobilizedanti human or anti mouse Fc specific antibody (Anti human Goat antiHuman IgG (gamma) mouse adsorbed (Invitrogen, Cat No. H10500) or antimouse FPc specific antibody (Jackson Immuno Research Labs inc. Cat No.515-005-071) were chemically immobilized on a CM-5 sensor surface usingstandard amine coupling chemistry) and used to capture the mAb fromsolution. Soluble human IL-3Rα was then injected over captured antibodyat various concentrations. Responses were subtracted from those from areference flow cell in which antibody was not captured, but otherwisetreated identically. The reference subtracted responses were thensubtracted from the responses from a blank injection.

The final corrected responses were fitted using non-linear regression toa model describing 1:1 kinetics, including a term for mass transportlimitation. The Rmax value was fitted locally, to account for slightdeviations in the level of antibody captured. Association rate (ka),dissociation rate (kd) and equilibrium dissociation constant (K_(D))were determined.

Antibodies were captured at 0.3 g/ml for 180 seconds

Soluble IL-3Rα was injected for 10 minutes, and dissociation wasmonitored for 30 minutes.

Soluble IL-3Rα was injected at 0, 0.62, 1.25, 2.5, 5, 10, 20 and 40 nM,with 2.5 and 5 nM in duplicate

Regeneration was performed after each cycle with a 90 second injectionof 100 mM H₃PO₄

The assay was conducted at 25° C.

scFv Kinetics:

To analyze scFvs, soluble human IL-3Rα was chemically immobilized on aCM-5 sensor surface using standard amine coupling chemistry, and scFvswere injected at various concentrations. Responses were subtracted fromthose from a reference flow cell in which IL-3Rα was not immobilized,but otherwise treated identically. The reference subtracted responseswere then subtracted from the responses from a blank injection.

The final corrected responses were fitted using non-linear regression toa model describing 1:1 kinetics, including a term for mass transportlimitation. The Rmax value was fitted globally, and association rate(ka), dissociation rate (kd) and equilibrium dissociation constant (Ko)were determined.

scFvs were injected for 10 minutes, and dissociation was monitored for20 minutes.

scPvs were injected at 0, 0.62, 1.25, 2.5, 5, 10, 20 and 40 nM, with 10nM in duplicate

Regeneration was performed after each cycle with a 30 second injectionof 100 mM H₃PO₄, 1M NaCl and a 15 second injection of 50 mM NaOH.

The assay was conducted at 25° C.

Antibody and scFv affinities are tabulated below in Table 2:

TABLE 2 Affinity dissociation constants of antibodies and scFvs AntibodyKD (M) parental murine mAb (7G3)  ~9.2 × 10⁻¹⁰ chimeric form of parentalmurine ~1.0 × 10⁻⁹ mAb) (human IgG₁) Superhumanized mAb (IgG₁)   ~1 ×10⁻⁸ Superhumanized mAb scFv ~1.4 × 10⁻⁸ CSL362 scFv ~2.2 × 10⁻⁹ CSL362(IgG₁)  ~7.8 × 10⁻¹⁰ CSL362B  ~4.3 × 10⁻¹⁰

Example 3 NK Cell Levels Following Administration of Humanized orChimeric Antibodies

Naive monkeys (non-human primates; NHPs) were administered a single doseof CSL362B or CSL362X1 via intravenous infusion. In a separate studynaïve monkeys were administered repeat doses (weekly×4) of a chimericantibody comprising the variable regions of the murine antibody used toproduce the humanized antibody (7G3) and a human IgG₁ constant region).Peripheral blood was collected at various time points and analysis ofNHP NK cells performed by flow cytometry.

As shown in FIG. 1A administration of CSL362X1 resulted in an initialdepletion of NK cells, e.g., about 6 hours following administration. Atdosages of 0.01 mg/kg and 0.1 mg/kg, this level had exceeded the levelobserved prior to administration by about 8 days after administrationand remained elevated until at least 22 or 29 days after administration.An increase in the number of NK cells was also observed at the 1 mg/kgdosage.

In contrast to the results described in the previous paragraph,administration of CSL362B resulted in depletion of NK cells, however theNK cell numbers did not subsequently exceed the numbers prior toadministration (FIG. 1B).

Repeat administration of the chimeric antibody did not substantiallychange the number of NK cells detected in circulation (FIG. 1C).

Example 4 Enhanced ADCC of Humanized Antibodies in the Presence of NKCells

Human PBMCs or NK cells were isolated and incubated with TF-1 cells inthe presence of various concentrations of CSL362X1. Effector Cells (E;PBMC) and Target cells (T; TF-1 cells) were combined to achieve a ratioof 50:1 (E:T Ratio) or in the case where purified NK cells were used aseffectors the ratio was 20:1. Cell lysis was measured using a LDHCytoTox 96 Non-Radioactive Cytotoxicity kit (Promega).

Specific Lysis was determined by the following calculation:

Specific Lysis=[Sample Lysis−Spontaneous Lysis]/[MaximalLysis−Spontaneous Lysis)]×100%.

Maximal Lysis was evaluated by addition of Extran™ to a finalconcentration of 0.75% (v/v). Spontaneous Lysis was that which occurredin wells with cells alone (no Ab).

As shown in FIG. 2A, lysis of TP-1 cells occurred in the presence ofPBMCs and in the presence of NK cells, however was substantially reducedin PBMCs from which NK cells were removed.

In a separate experiment, leukemic cells from two different AML patientswere used as target cells. In this assay, a single concentration ofantibody (10 μg/mL) was used and purified NK cells were added togenerate various E:T ratios. FIG. 2B shows that the higher the number ofNK cells to target cells (peripheral blood blasts from two different AMLpatients) (i.e., the E:T ratio), the greater the specific lysis of thetarget cells by the humanized antibody.

1-16. (canceled)
 17. A method for inducing lysis of leukemic cells in asubject with acute myeloid leukemia (AML), the method comprisingadministering to a subject suffering from AML an isolated or recombinantantibody that is capable of specifically binding to interleukin (IL)-3Rαchain, wherein the antibody comprises: (i) a light chain variable region(V_(L)) comprising CDRs 1, 2 and 3 as set forth in SEQ ID NOs: 2, 3 and4, respectively; (ii) a heavy chain variable region (V_(H)) comprisingCDRs 1, 2 and 3 as set forth in SEQ ID NOs: 5, 6 and 7, respectively;and (iii) a heavy chain constant region comprising amino acidsubstitutions S239D and I332E according to the EU numbering system ofKabat.
 18. The method of claim 17, wherein the antibody is a humanizedantibody comprising: (i) a light chain variable region (V_(L))comprising an amino acid sequence according to SEQ ID NO: 8 and a heavychain variable region (V_(H)) comprising an amino acid sequenceaccording to SEQ ID NO: 9; and (ii) a heavy chain constant regioncomprising amino acid substitutions S239D and I332E according to the EUnumbering system of Kabat.
 19. The method of claim 17, wherein the heavychain constant region comprises a sequence set forth between residues121-450 (inclusive) of SEQ ID NO:
 11. 20. The method of claim 17,wherein the antibody is a humanized antibody comprising a light chaincomprising a sequence set forth in SEQ ID NO: 13 and a heavy chaincomprising a sequence set forth in SEQ ID NO: 11.